I’ve tested those flags (both) and they work for my game in Firefox.
So if anyone comes across this in the future, try out preventDefaultOnPointerDown and preventDefaultOnPointerUp, or scene.detachControl(). Either of these will let mousemove, mousedown, and mouseup all the way out in Firefox.
I don’t know what is up with that old pg (which doesn’t change with those) but none of that effects my game.