It's the question of if she needs to remaster Wizard's Reach (Ignem) if she has already mastered Wizard's Reach (Ignem). Which to my mind is very different than your question.
These are both answers about how one could sensibly interpret the rules differently. But I'm more interested in if anyone sees a reason to actually handle it differently at the table. Would you really tell the player that they can't use their mastery score for their target group version of seven league stride if they went to the trouble of reinventing the spell to get a new group of non-warped targets?
No. If there were an issue, I'd tell the player before the magus wastes his time, because the magus would know better.
Neither way of ruling is better. Each provides different benefits and restrictions.
If both spells share a mastery ability, then you might be able to as you describe, but you lose the ability to learn BoAF with two small but different set of masteries. Maybe one is my "combat penetration" spell and the other is my "finesse and showy" spell. Or something. So, in any given saga, making this decision has implications.
There's a legitimate 3rd way to rule, which is that even if the spells share a mastery ability, relearning the spell doesn't let you change who it is designed for, beyond one specific target, because that list is tied to the singular mastery ability.
A eloquent way to phrase a statement about different wizard's reach spells that target spells of different forms or spells that are with the exception of whom they do not warp identical that does not use the word version eludes me. One could reasonably expect that even if the "versions" in the two uses were much different from one another they'd both statements would use the word "version" because it's the natural way to convey the information and expecting the author(s) to modify their language to prevent this particular ambiguity is unrealistic.
As to why there is a significant difference; in the case of the wizard's reach spell the actual spell description is different (or would be if you wrote out an specific spell description) one changes ignem spells and one targets corpus spells. In the case of a spell reinvented to change the potential targets who would not be warped you would use precisely the same spell description, you'd give the spell the same name. Warping from powerful mystical effects is an afterthought.
If you have a book on spell mastery for Ball of Abysmal Flame a magus could read it and gain xp in spell mastery for BoAF regardless of whether or not their BoAF spell is calibrated not to warp their apprentice. If you had a book of spell mastery on Piercing the Infernal Veil you couldn't use it get xp for spell mastery for the spell Piercing the Faerie Veil. Form specific spells are like the case of the realm specific spells, they're just not labeled as clearly.
Before I posted I considered elaborating that one would, of course, tell the player before hand, but I decided against doing so. I thought it would make my writing more confusing, it would take more time, and I doubted that people would interpret my post as suggesting that anyone would let the character's do something stupid and thereby screw the players.
I was wrong. sorry.
Yes, that's coherent from a setting and rules perspective, but can you think of a benefit to deciding on that interpretation for play?
That's your opinion, which you can argue with your troupe. But on what is it founded?
ArM5 p.168 Powerful Mystical Effects is brief. But it clearly speaks of a "special version of a Formulaic spell" to invent, not of afterthoughts - so your hypothetical "actual spell description" would have to include "doesn't warp Kuno the shield grog by its power", or wouldn't it? Where would you put that information otherwise?
So it might as well be in the lab text for the spell, and require specific mastery books. This is a troupe decision.
opinions- would it/should it be possible for someone with a virtue like hermetic architecture to designate a non-warping room for room target? If not should that be possible with a different virtue (existing or new) and if new how signifigant a virtue would that be?
Rereading page 168 my take is that it would be fine, provided we're talking about the same thing. You're worried about warping the room itself rather than anything that might be inside it when the spell is cast, yes?