Gear change overrun setting.
With a mechanical indexed setup there is a natural overrun when changing down (up the cassette - smaller to larger cog) which helps initiate the gear change and keep it smooth. i.e. the cable pulls the derailleur a little bit past the ideal position for the next gear but when the rider releases the lever the derailleur falls back to where it should be. AXS simply moves the derailleur to the next ending position which makes the change clunky under power. If AXS mimicked the mechanical shift with a little overrun before settling in the ideal position that would fix it.
It would also help with my XX1 AXS derailleur which has developed play in the parallelogram and now changing 10T to 12T is unreliable without changing down twice (10T to 14T) then going back to 12T.