I’m mo expert on the 8x, and certainly not on any sort of CBA. I watched the video very carefully and it seems to me that when the accordionist seems to reach for the master bar, he’s actually doing something else and those are not the events that produce a pitch bend.
I used to have an amateur band, in which I often had to supply the sound of a clarinet, complete with trills, ornaments we referred to as “Krechtsn,” and pitch bends, usually downward. I accomplished this with an acoustic accordion equipped with MIDI and a glide pedal.
My FR-4x has pitch bend by default built into the uppermost row of bass buttons — not the most convenient spot. If I had to do what I did then with the 4x, I’d need a Greg V Pedal to do it conveniently.
So, hang on to those chin switches. I know one guy, an 8x player, who does pitch bends with them, and he’s happy with the way it works out.