Mousemove events that occur over disabled controls are not always available to scripts. It seems to depend on which control. The events are correctly fired when the controls are enabled.
Created attachment 175284 [details] Shows the problem
Tested with Safari Version 6.0.2 (7536.26.17)
FWIW, useCapture=true w/ addEventListener didn't solve the issue for me.
Opening the test case in Firefox does not exhibit this issue.
<rdar://problem/13997363>
I am not able to reproduce this bug in Safari 16.5.1 and STP173 and hovering over all disabled control, does update x,y coordinates.
Closing based on Ahmad's testing.