If I take Enchanting Music, Entrancement, Strong Faerie Blood, and Greater Sympathy, does that mean my character's parens has a 200 InVi lab Total? Shouldn't the character start with 200 levels of spells from one season of training?
First, maybe such a character picked up those Supernatural Virtues after their Arts were Opened. Second, maybe the character's parens never taught spells, just letting the apprentice learn from laboratory texts while teaching what the parens thought would be more important things to teach.
I will swear I read a rule that flaws taken in character creation don't count towards ordeal bonus - If you look at the Cabal Legacy minor flaw box on page 20 of The Mysteries, it says "Flaws acquired now do not later count as past Ordeals"
So it is possible to load up on a mystery cults virtues and take balancing flaws during character creation, but it won't give you ordeal bonuses.
In one game, we tried to open the arts of a Shapechanger who had Second Sight - we got an InVi total of 80 by having our Bonisagus use his leadership to get a lot of lab assistants adding their Int + Magic Theory, opening the arts, and then handing the apprentice over to an Ex Miscellanea for fifteen years of training. If anyone complained, the Bonisagus would have had to use their right to take other's apprentices to take the apprentice back and then complete their training - but as Bonisagus accepts fostering as a practice, he could have outsourced this.
Why? All you need is anyone the parens got a hold of to have a Teaching Source Quality that is reasonable and that the parens could get to help, such as a companion at the covenant. You already get +9 for an individual, and +3 is possible through the lab. So 9 more from Communication, Good Teacher, Apt Student, Teaching, and Teaching specialty would be enough to teach two Supernatural Abilities. Meanwhile, Faerie Sympathy can be picked up in other ways.
This is certainly one of those areas where the various parts of the rules don't work together especially well.
If one takes the rules on Opening the Arts from AM5 pg.107 strictly, then all of the Ex Miscellanea traditions require excessively skilled masters just to perpetuate themselves, at least by the standards of a lower-level game. Ex Misc are moreover just the sorts of magi to work alone and without possessing elaborate laboratories, so reaching an InVi lab total of 60 to retain the tradition's Supernatural Ability requires very high InVi.
They are written over eight plus years by varying authors, which also makes them hard to read.
Do you assume, that Ex Misc just search until they have found a Gifted child with exactly the Supernatural Ability required by their tradition, and only then open her Arts? I fear, that most Ex Misc traditions would have died out in a century or so with this as their only method.
As we discuss the options from Apprentices here, I refer to:
If one were to follow RAW strictly, Ex Misc would either:
Train the novice in the supernatural ability, without penalty, and then open the Arts using a high lab total.
or
Open the Arts normally and then teach the supernatural ability, taking a penalty of 15 or more to the source quality.
Neither of these explains the required Flaw common to each tradition.
Mysteries could be a third approach but Ex Misc traditions do not in general possess mystery cult lores.
It sounds like we agree that the proper approach is to wing it when the rules don't quite work. That's how I read the quote you give from Apprentices at any rate.
The corebook rule works at preventing Magi from doubling on with hedge traditions but I wouldn't like it to require an Archmage to open the Arts of someone just because they have Second Sight and Faerie Blood.
Because you are saying the character gets it later. So that's an initiation according to RAW. So, let's see what the parens must have, show me what the parens must have to initiate.
In the attempt to avoid munchkins they force munchkinism and remove options for fun and storytelling. Kinda like RoP:M, it spends pages explaining the Magic Realm and travel, then makes rules for it impossible lol.
Does a parens need to have a high lab Total to preserve a supernatural quality like "Lycanthrope"? Since the underlying rule is "if a player wants it, make it impossible", should opening arts remove the lycanthropy?
What do you understand by RAW? ArM5 doesn't say, that the rules in p.106f Training Your Apprentice are the complete and only ones ever to govern that subject. There were no errata needed to it, when Apprentices appeared and added to them. ArM5 didn't need errata when HMRE or TMRE appeared either, but certainly didn't cover Hedge Magicians or Mysteries before.
Then you can't conclude, that "the character start with 200 levels of spells from one season of training". ArM5 p.106f Training Your Apprentice need not be - and is not - all the rules there are on the subject.
This quote from Apprentices is RAW:
And it says - RAW - that "the troupe should decide if an apprentice of a specific tradition learns the House Virtues and Flaws through one-on-one association or through a process similar to a mystery initiation like the Mystery Cult Houses". So, indeed RAW says "the proper approach is to wing it" here.
Ars Magica books just cannot cover all the details of magic and Mythic Europe. It is not D&D or such, where 'RAW' can be all-inclusive. Its world is far too vast for that.
As also a D&D player, I take offense that you're implying D&D is dumb enough to think it can RAW all-inclusive. The entire DM section reads like "So the rules don't work, huh??"
Your statement about RAW here is pretty blatantly incorrect. You really need to read the rules a bit more before making such claims about RAW. Either that or you're stuck with your logic between necessary and sufficient conditions. RAW says one way is via initiation. But it also provides several other ways, including two in the core book itself. Here are the ways I can think of off the top of my head of picking up a Supernatural Ability after your Arts are Opened to Hermetic Magic: good Twilight experience (core book), being taught it (core book), initiation (HoH:MC, TMRE), Opening in another tradition (HMRE?, RM), transformation in the Magic Realm (RoP:M), and maybe picking it up during training as Ex Miscellanea (App). So, no, picking up a Supernatural Ability after Opening your Arts to Hermetic Magic most certainly does not imply an initiation.