not just Moog, even an old ROMpler or something is different with an extra generation of conversion. It all changes the sound. A good, 24/96 transfer of a poorly recorded cassette doesn’t sound as good as the same cassette played on the same deck through the same monitors. Whether it’s better, worse or just different is completely context dependent and subjective, though.
Anyway, the difference between direct analog monitoring and passing through the OT (24 bit, no timestretch) is pretty far from “butchering” as far as I’m concerned. It’s minor.
Analog synths I’ve passed through the OT before:
Juno 6
Matrix 1000
Mother 32
MI Anushri
Kijimi
Jasper (WASP clone)
x0xb0x (with NOS ICs and transistors)
Roland RS-09
The only synth the Octatrack actually made sound different enough to be a problem for me was actually a Kawai K1. the analog stuff still sounded perfectly fine, just ever so slightly “smaller” for lack of a better word. In the room the would sound a little less impressive; as part of a full mix, the coloration from the Octatrack sometimes made the work better; the Mother 32 in particular had a way of being kind of overbearing (part of the reason I ended up selling it back to the friend who sold it to me) - good, but also “hey there’s a Moog with some other stuff around it” rather than “there’s a mix that has a Moog in it” and the Octatrack tamed that a bit. The Anushri handles the Octatrack converters the best of the bunch. In all cases except the K1 it’s been really minor, and this is in actual practical use (i.e. with filters left on), much less trying to make the OT as transparent as possible.