spanishbuddha I think that the link to the loud note firmware is supposition only, so you can test it if so inclined.
You are quite right, my friend. I did that test, using PTQ as the MIDI velocity display and no sound (because my daughter was playing violin) and 🎉 I noticed the same problem that @porco_rosso described! I tried to play random notes with arm-weight technique, falling from about 4" above the keyboard and most of the time I got velocities around 120+ and occasionally around 105 and around 88. This is a NU1 with official firmware (no-loud-note-fix one).
Now, you may wonder why I never experienced that while playing and the answer is pretty easy. To achieve these 120+ velocities I had to do the technique described above, which after only a couple of minutes of doing made my fingertips hurts. I never play with those velocities, and certainly never for so long. During that time I must have played about 50 notes, and only about 5 showed the problem unambiguously, so if these statistics are correct, no wonder it went unnoticed for so long.
In any case, I think this is a shocking find! If you haven't already, @spanishbuddha I suggest you try it that way too and perhaps suggest to the PW thread also. You really have to "bang hard on the keyboard" to see this happening, your "banging" must be at a level of surely triggering 120+. As a speculation, the problem could be that on such velocities the downstroke is so fast that it misses the second trigger and reaches it only later after rebouncing from the keybed, resulting in a lower apparent value.
Now, as I said, I experienced no sound, so I don't know on that side, I'll give it a try another day.
PS: I also noticed that the NU1 sends aftertouch signals while doing partial note release, so maybe the loud note fix use those?