https://www.musical-u.com/learn/is-ear-training-useful-if-you-can-already-play-by-ear/
Ear training is not simply for learning to play by ear. It is about hearing more detail in music and understanding what you hear. These benefits are just as relevant and useful to a “play by ear” musician as a “sheet music” musician! https://www.musical-u.com/learn/is-ear-training-useful-if-you-can-already-play-by-ear/