Assuming from demonstration video XorgTablet was written & tested specifically for Samsung Galaxy Note 10.1 which has wacom-driven stylus; such device can detect stylus hovering over canvas and stylus has 1024 pressure levels (afair).
When you’re using tablet without this functionality you do may not have “hovering” level of pressure. So when you touch screen even slightly it just sends “pressed” -> like mouse button with its left button clicked. Can you confirm your device support hovering? As far as I can tell it probably doesn’t.
If you’re referring to mouse as real mouse: when you setup Gimp to use NetworkTablet0 as input real mouse clicks stop working, I can confirm this, same happens to me (any Gimp user with real wacom tablet can confirm this as expected?).
If you’re referring to mouse as tablet input firstly check APK from #1 (it fixes pressure detection for Note 10.1), if you cannot install it you must have adb on your desktop and do:
adb uninstall com.gimpusers.xorgtablet
and then install this APK.