What I’ve read is that DBX noise reduction was to blame, not tape machines, but in the liner notes, FWIW, there are no complaints to back this up.
In the liner notes, Fagan and Becker do mention "our splendid double Magneplanar monitor. system and newly acquired and fabulously expensive Audio Research D-76 tube power amps", which would reinforce the assertions about Becker at least being an audiophile.
I've only heard the 1999 remastered cd of KL and have never found the sonics detract from enjoying the music.