One of them says:
For the purpose of "learning", any note other than C, D, E, F, G, A, or B is WRONG. (no exceptions)
When it comes to "playing", the only WRONG note is one that you didn't intend to play.
to which I feel like adding: When it comes to "jazz", the only wrong note is one that, in hindsight, you wish you hadn't played.
