I chimed in on this topic in the original thread. I had tried a variety of discs and files, to see for myself what others were seeing. For me, it happened on some tracks and not on others. Some of the discs I tried were ones that I ripped myself. These did not produce the fade in.
Some file tracks I tried, from a flash drive plugged into my Oppo, exhibited a fade in, but not others on the same playlist. Whenever it occurred, it was a few mS at best, and resulted in not much more than part of the first note.
None of the tracks ever missed an entire first word or two. In my experience, this "fade in" was too quick to miss more than a part of this first note, and this was about 5% of the tracks.

The common thing I noticed was this happened whenever there was a loss of audio in between tracks and my 976
had to reacquire the audio signal.

I admit, I mostly use my 976 for movies and TV.
If I were predominantly using for music, and I turned off the lights, closed my eyes and focused on specific music experiences, I'd probably connect to one of the pure analog inputs that would eliminate this very small % of fade-ins.