Tap and hold always worked for me to get the dialog in matchbox on pdaxii13.
This is the first time I have heard of, or tried right click on the taskbar.
Fn+tap or right click with a mouse, (I plugged in a mouse to try this, to be sure my "Fn" key wasn't borky), makes the pointer disappear and gets no response from the taskbar.
Clicking the stylus again makes the pointer re-appear.
Also, I just now noticed, if you tap anywhere on the desktop, and then press and hold "Fn" the pointer will disappear.
The last statement has nothing to do with the taskbar, but it is something I have just discovered.
EDIT:
nevermind about the pointer disappearing after holding the "Fn" key, it disappears after a certain amount of time anyway...
Enclosed screenshot is showing tap and hold on the taskbar.
Jon