I agree with you. He wasn't telling the contestants how they should sing the song; he was telling them how he would sing the song. But, the good ones benefitted from it by learning something about how country music is sung.
Thing is, those who are left are pretty good. I'd really, really like it if Ace, Bucky, and Kathy go next. (even though Ace maybe has some hope with country)
Bingo! He has his own style and they need to have theirs.