1) "Does this actually produce results I can see in my students or feel myself?" and,
2) "If it works, why? Is there any logical, non-experiential reason to think this is true"?
Either of 1) or 2) by themselves are potential wrong turns that lead an actor or a pianist down months or years of wasted time. 1) "This worked for me last night" is NOT solid. "The logic of this idea is impeccable" is better. But if it doesn't work in practice, something ain't right. It must be peccable after all.
Teachers should question EVERY single idea they put out to students, do their best to never put something out there as "fact" that isn't.
I'll leave it there. I'd like to keep posts short. Thanks for reading!