What’s the difference of sending data to evf or to rear screen? Or the 90 doesn’t make 120 while on liveview?Probably because the processor has a lot more to deal with in a mirrorless camera. Sending the image up to the EVF, and doing all of the computing related to autofocusing straight from the dual pixel image sensor for example.
I turned the screen off. Left it always on the evf and assigned fn bt to change between evf and screen.You can have it less sensitive or less laggy, which do you want? The reason it's so sensitive is so that it can sense you bringing the camera up to your face even before you have it completely against your face to reduce how laggy you perceive it to be. If you made the EVF sensor less sensitive, it would be more laggy, as it wouldn't start switching to the EVF until the camera was closer to your face.
Yes ideally the EVF would just turn on faster, but I assume Canon has done everything they could to make it change over as fast as possible, so they had to also make the EVF sensor extra sensitive to reduce the perceived lag.
So again, with the current technology, you have to choose one, less sensitive or less laggy. I'm glad Canon made it as sensitive as it is to reduce the lag, even if it is occasionally annoying when it switches to EVF because my hand is too close to the sensor when using the touch screen.