Hmmmmm, what electronic communications are required between the lens mount and sensor in order to read sensor at a higher refresh rate?
A Genuine question though.
Unless it is a requirement for the lens to refocus for every sensor readout operation. This is An insane requirement if true.
The problem is more a latency problem than anything else. Higher com speeds reduce that latency.
AF is a stream of interactions between the camera and the lens. If the commands can be passed faster, then the lens can AF faster. I am just guessing as to how the actual protocol works, but it could be like this:
Camera: adjust focus +154 units
lens: done
Camera: adjust focus +17 units
lens: done
Camera: adjust focus -2 units
lens: done
(picture taken, now we start tracking)
Camera: adjust focus -1 units
lens: done
camera: adjust focus +2 units
lens: done
and this is just AF....
something similar will be happening for IS at the same time.
the faster you can communicate, the faster the response and the smoother the tracking for AF and IS.