I can't reproduce with normal (logitech) mouse, did you already make conclusion that it only happens with apple pointing devices or am I missing something?
Thanks, a good point I hadn't thought of. Just tested a MX Vertical but it makes no difference.
I re-tested all combinations and got the same results.
I can only imagine most users simply don't notice the additional delay but I deem it unlikely in regard of the extent (at least with the internal trackpad).
It's the worst when switching from my Mac Pro to my MacBook Pro as the delay is doubled (see attached values).
(I got the estimated values by slo-mo recording my screen and my mouse/finger movement. Then counted the frames from first mouse/finger movement to first pointer movement)