I agree about arranger credits; common and unfortunate oversight (?). Case in point: the Blakey clip that pryso recently posted features a fantastic arrangement by Freddie Hubbard. I don’t think that this is credited on the LP at all. Another example: perhaps a result, in part, of a bygone era when the orchestra leader was often also the de facto arranger, but was credited on the album cover as simply and for example: "Frank Sinatra With Billy May And His Orchestra". As you say the arranger is a major element in the recording; sometimes the major element.
Very astute comment re Kenny Drew Jr. Son of the Kenny Drew he began as a Classical pianist and has indeed performed quite a bit of Bach.
Not exactly definitive but as you point out he certainly understands Bach:
https://m.youtube.com/watch?v=28JU935pF7E