Maybe I'm odd but I don't find these sorts of tips discouraging at all, however it does annoy me when big obvious problems get ignored this is destroying and far worse than pointing out tiny errors.
I agree - having developed lots of bad techniques and THEN having a teacher who wasn't a flute specialist teach me some things that were also bad habits... and THEN having to get rid of them all. It can be soul-destroying especially when you've worked so hard. So I am extra careful that as far as possible nothing bad gets ingrained... I think it's particularly important if a student is talented as (IMO) it's doubly sad if such a child gets held back by poor technique that could've been corrected easily (some things are more difficult to get right than others but it's terribly sad when basic things which are just as easy to do right as to do wrong get ignored).
It isn't easy to strike a balance between fun vs playing right, but (IMO anyway) it's much nicer and more helpful to have a reason ("I'm asking to do this because...") rather than technique being addressed as "this is the way we do it". Depending on how vital something is, the emphasis is changed - and the methods used to get it right and the tolerance of not getting it right is flexible. It's possible to have fun and learn correct technique at the same time!
