P.S.
Yes, I know,
"Nothing is impossible for the man who doesn’t have to do it himself."
-A.H. Weiler

Right now, when the mouse crosses from the right monitor anywhere below the bottom of the left monitor, we move it to just above the bottom edge of the left monitor.

So in this situation, if you move the mouse over at the blue arrow, it's pretty close when it crosses over. If we change it to purely percentage based, that's around 50% up the right monitor, so then it would end up half way up on the left monitor, which is an unnecessary jump up.

There are other scenarios that make using only percentage weird too, so until we can spend some time finding all of those edge cases and making exceptions for them, this isn't something that we're likely to implement.

take a look at the attached screenshot.

We are in control of where the cursor ends up, but we need to make sure that all of the logic is well thought out before we can switch it to a percentage based system. It's not as simple as just saying "it was 60% down the screen when it left, so put it 60% down the target monitor." We are still planning to implement it, but just want to make sure that we do it right the first time.