It's somewhat more complex than that. Not so much warmer as a result, but more "one note".
Meaning that in particular, piano, and interestingly, snare drum, sounded "boxy" from one LP to another.
Because cymbals and electric guitar maintained or even improved re bite, shortcomings weren't noticeable, and indeed initial impressions were of improvement.
But once I started latching on to this boxiness, the nagging sensation of SQ overall having worsened started increasing.
I'm going to put this down to either a bumped resonant frequency or a smearing of leading edges.
I find it fascinating that an affectation or imposed character can be not noticeable early on, but come to the fore to actually dominate impressions of overall sound.