He mentioned awhile ago that he has techniques he trained from the stele and hasn't actually put into use yet. Don't treat it as an asspull when you just forgot the details. Plus, it'd be ridiculous if we had to sit and watch a character train up each and every one of their abilities before using them, so I don't know why people freak out about that to begin with. Especially in a cultivation setting, where the same move almost never works twice on an opponent - and an opponent who's prepared to deal with it will just never be hit with it regardless. Guarding your secrets is the same as guarding your life.