To be clear, the above is a guess at Boney's motivations. It also makes sense for the in universe flavor, but I assume making it so it actually gets used was the primary intention. Otherwise, it would be a bitch to handle. Either Boney has to stop for a vote each time a chance to use it comes up, or else decide himself and get bitched at for a miscast (and understandably), or allow super complicated conditional action plans and probably still get bitched at.
The first option kneecaps the pacing and is unfun for everyone, the second option produces lots of strife and is especially unfun for Boney, and the final option makes GMing a chore, probably still causes lots of strife, and is still unfun for Boney. I suspect Boney was quite glad that the thread didn't really go for BM (I think even learning the first was a result of the dice deciding Mathilde was cleared now while she was trying to learn a bunch of random spells). And then the staff allowed the option of BM that also avoid this issue, at the cost of restricting which spells can be used (at non-BM difficulty). Which I suspect is one reason why an effect that powerful even turned up, for all that the roll was quite good, that first try staff is still comparable to
Kragg's work where the impact on Mathilde's style is concerned.
@Boney Out of curiosity, did you have any plans for how to handle it if the thread did decide to learn BM spells back when Mathilde couldn't safely cast them? I don't think it's going to happen nowadays, but I don't remember what the sentiment was back then. But it sounds like a total pain for a GM, and I really don't know how I'd handle it.
(I'm also curious if I got your motivation/thoughts correct, and whether that was a concern)
