i think class a/b in so many channels in such a dense package... why
I think the decision may have been driven by many of the Onkyo "faithful" who really liked the big, high powered AVR's they had from the mid "aughties" to around 2015 - they put out ample power (140W rated, but 165W@8ohm stereo, measured), handled low impedance loads without major issues (even though not rated for them) - their amps were highly regarded for good reason, and they were ClassAB traditionalists.
I for one, had two generations of the flagship "beasts" - and such an AVR would probably cause me to simplify my system, put away my ClassD power amps, and just rely on the AVR alone.
So from the Onkyo and Integra side, it leverages a long lasting reputation for muscly class AB amps going back to the 1980's.
When Onkyo purchased Pioneer, they moved their flagship models over to use the Pioneer SC series chassis - ClassD. Now this, although excellent, was somewhat less powerful compared to their previous ClassAB offering - rated circa 120W... as opposed to the earlier flagships 140W - but I believe it also had less headroom - so peak output was much more constrained too.
They could in this generation, potentially re-engineer the Pioneer models for Class D, and re-release the SC series of course... But I think the dollars and cents kicked in, and they had to make some difficult decisions - Pioneer as the "Junior" brand lost out to the marketing advantages for Onkyo and Integra (that's just my thinking!)
I would hope to see the eventual release of a true Pio chassis... something that runs ClassD and perhaps even a switch mode power supply.... perhaps the SC-LX906 of 2025?