As an update, I added new commands by recoridng the remotes volume up/down. Now hold to go up and down works but its insanely unreliable. Its very slow going down by one tick every half second, but then randomly will skip ahead by like 5 ticks at once randomly and inconsistenly. So closer to a solution but still not working well at all.

In device mode it does the same thing as in activity mode, long press only does effectively a single volume down instead of continuing to go down as long as I hold it. The AVR is a Denon AVR-S570BT