That processing causes heat, and heat lowers image quality locally on the sensor. So Canon wants to patent the idea of distributing the computing across the sensor, and even load-managing the processors so that it doesn’t develop hotspots particularly in the spot where you’re trying to focus.
What is sometimes most revealing about these patents is the timing history. This one was submitted in October 2020, a few months after the launch of the R5, as Canon finished its first firmware updates and appears to have been gearing up for the follow-on. The technology would have been in development for at least months prior.
Canon announced already the coming R3 camera that will have a stacked sensor.