I know about this issue but i start using ES becasue I thought that X-H2S is designed specially for shooting moving objects as it has sensor with the fastes readout on a market and drive modes 30fps and 40fps avalible only in ES. And in ES you doesn't have blackout, freezing or low frame rate in evf during continous shooting.
But i'll try do few test to chceck 30 and 40 fps and also MS, becase to date I used only 15 and 20fps.
Me friend who shoot also airplanes with Canon R5 use ES and had problems but related to the IS which was fixed by updating lens firmware. That's why i strated suspecting that may OIS can do bad job during handheld paning.
I'm guessing what for example do the subject tracking. I found that after turn it on, you can't change metering mode, can't change limiter in camera, and maybe there are more settings blocked, maybe it changes how OIS work during paning?