I identified 2 things going on:

1 -- A noticeable variety of soft playing notes snap to midi velocity "1" (watching the midi as I play). Basically I could get down to velocity 6 (out of 127 max) and then it jumps down to 1 for everything softer than that. This was true for all touch curves except "fixed".

2 -- Many velocity sensitive instruments map velocity-1 to dead silent (basically all the pianos, a few of the e.pianos, and a various mix form the "sub" group). While others had an audible "minimum volume" for those soft notes (the WR's and RD73 for example).

This is pretty annoying when you want to play something delicate on piano, as you'll just lose notes randomly.