The issue with adverse yaw in MSFS is straightforward:
The MSFS flight model is modelling each control surface as a flat plate independent of the wing/tailplane it is connected to. If the plate is flat in the airstream, it generates no lift or drag. If the plate tilts down, there will be up-thrust and some drag. If the plate tilts up, there will be down thrust and some drag.
The issue is the drag calculation is symmetrical whether the plate moves up or down. That works kinda ok for flaps that only move down, or elevators moving up & down, but identical drag from both ailerons won’t produce any yaw when you bank.
The FSX flight model has an additional optional ‘hack’ parameter that adds a ‘yaw moment’ for any movement of the ailerons, Asobo took the sensible choice of deprecating a slew (haha) of hack parameters from the legacy flight model, but this had the unexpected side effect of cancelling adverse yaw.
Sim Update 5 coming on 27th July has new parameters added back into the SDK so you can specify differential drag when then ailerons move up vs. down, so devs can program in whatever adverse/positive yaw they like.
This issue seriously affects gliders, and I’m a glider developer. Actually more problematic is the same issue affects negative flaps so it is essentially impossible to model flapped gliders (the solution is to introduce some fly-by-wire and manipulate the speed brakes but this has only ever been done on the FSX ASH25).