If im making an NPC, i much prefer carving out what skills they should have first, THEN i take their background as a guideline for how much XP per year they could be expected to have gained (a bookworm magi with superb access to books might get 80+XP per year while a labrat magic item specialist will mostly have gained XP from Exposure and so might have an average of 10-15 per year) and "simply" divide total XP by that, giving a rough calculation of minimum age. Add a few/some years to that to keep them from being supercharged and allow for later(or emergency if you forgot something important) finetuning... Done.
This means you dont have to redo a NPC if you find that s/he became far too powerful or a total wimp, meaning you have to change age and go from there, a very bothersome way of doing it.
As any assertion in a world where words can lose their meaning if one of the people talking decide to...^^. What people say has no more value than what you want to put on it. I've never claimed to be the Truth ^^.
I expressed MY point of view about NPC just after apprenticeship or any age of creation.
Take the template of mages? any of them is weaker than the magus we discut here.
And about the rest, yeah some SG will optimize NPC but if PCs must have a chance to win (battle/tribunal...), you let them weak in some things (combat/debate/...) which are their weaker spots.
PCs don't have the problem: they want to go better.
And for the rules: the PCs follow them at creation, so does my NPCs. After creation, both follow their life. But, in my troupe with 4 SG of 6 players, i can say: we enjoye 4 adventures par year, and is not uncommon to have 75xp per year. I can't, as a bSG, do the same for NPC because they would have no weak spot, or would have so much strong spots that they can't be hit in weaker spots.
Where NPCs can "easily" have access to rare books (high level) or teachers (parma in our saga is limited to 3 without teaching), PCs have ideas and intelligence the NPCs may have but i don't give to them, because i can just copy the PCs for NPCs.
And about words, just for complexity: what is "to be better"? better fighter? better speaker? better politician?
So you see... it's all about our feeling. And i feel that despite all my NPCs powers - quite optimized because i'm optimisator 3000 according to the aSG - the PCs are better.
And... i like that. They are the PCs and that's fun.