Touch (Devices Window) in combination with Mouse/Touchpad outputs NIL

not a biggie, in fact I’m not sure if this is a bug or a feature:

Touch (Devices Window) works great on my multitouchscreen, as long as I don’t touch the external mouse or the internal touchpad of my laptop.

as soon as I do, all outputs of Touch do output NIL, even if I have several fingers on the touchscreen.

can you be more specific about the hardware you’re using? works fine on the setup i’ve available here - a surface pro.