Tapping does cause retard - I said advance drops, which I can see is confusing. My bad.
At around 22% TPS it is using 38° advance and there is mild activity on the knock sensor. 3% more TPS and ign is at 16° with no activity on the KS. That clearly aint max timing for that load....!

The CAS chopper wheel is on the crank inside the crankcase, and the pickup bolts into the block with no adjustment