Even the 8000's haven't had nearly enough heat sinking or power draw for their claimed output power in class A.

My guess is that they ran the small-signal stages in A, and biased the output stages for class A up to something like 20 watts, and then switched into A/B.

Living room: 818v3, Parasound A23+, Maggie 1.6
A/V room: 861v8, DSP7200SE L/R/C, 4x DSP320 surrounds, ID41 + Roon, UHD722, Prime+PS