Hey, I would say that it's a mix, and now things have been formalized a lot in the realm of Jazz (that's a whole subject on its own). I would say that classic

Hey, I would say that it's a mix, and now things have been formalized a lot in the realm of Jazz (that's a whole subject on its own). I would say that classical training can definitely help a lot from an interpretation standpoint, there are many technical and harmonic concepts that definitely hold. Some classical repertoire probably helps more and has more parallels to Jazz too. Something that I have to emphasize though, is that you can be quite proficient at playing classical piano and also have a not very sophisticated harmonic understanding ("interpreter v/s composer"), that understanding is required if you're doing Jazz. Some examples of non-classically trained Jazz pianists that are incredibly relevant: Thelonius Monk, Art Tatum. On the other hand, many important Jazz Pianists had extremely relevant classical training. Jarrett being one of the greats and I would mention Brad Mehldau as someone who's extremely influenced by classical as well, and who's still alive and expanding the language of Jazz. Regarding the "training methods", I would say that the classical training methods are problematic if they're tried to be applied to learning jazz. The successful student will have to adapt and drop a lot of them to learn improvisation, which in the end is the essence of the jazz language.