Even so, the written composition of Chopin or whoever has an authorative status of a kind that is not present in the 1954 definition

The beauty is that there will always be new interpretations whilst not a note of what Chopin wrote will change. Even so Chopin was part of a Tradition nevertheless and his pieces can be used for effective Improvisation, or just exploring their subtle nuances. The other beauty is that not everything in any given tradition has to change - if it changes fine, if it doesn't then that's fine too. The important thing is that it was the result of the change and mutability inherent in any musical tradition.

I mean, who's going to mess wityh Teo Macero's definitive edits of Miles Davis that comprise Bitches Brew?

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I know a violist who has one beautiful old violin; when he plays classical stuff on it it is a violin, when he plays Folk on it, it is a fiddle; same instrument, but it becomes different depending.