I played around with this a bit… I’ll have an update with 10.0.5 next week that hopefully should resolve it.
I could not get frame:RegisterForClicks("LeftButtonUp", "LeftButtonDown") to work either… would not fire the pre-click events with ActionButtonUseKeyDown set to 0.
I ended up just avoiding it and using MouseDown for this disenchanting behavior, which does seem to fire no matter what.