Drag Threshold doesn't seem to work for mobile

I'm setting up a standard mobile joystick UI. Left joystick moves the character and right joystick looks around. I lowered in the Drag Threshold in the UI event system to 1 (from the default of 5) so a drag begins right away as opposed to waiting for 5 pixels to be dragged. When testing with mouse in the editor, this works fine. With a mobile build (android), a certain drag threshold is still there.

Any ideas as to why?

PS. Once a drag is started, the accuracy is seems to be ok, it's just...

Drag Threshold doesn't seem to work for mobile