Snoopy 1.0 from rapps erroneously does not hide the taskbar when switching into fullscreen mode

VBox4.3.40, VBEMP, 800x600 desktop resolution 32bpp
Install Snoopy 1.0 from rapps and install the main app
In the main menu there is a checkmark "Full Screen" to switch into fullscreen 640x480

Expected result
When checking the checkmark, the app should switch to fullscreen and the taskbar should be hidden, like
2k3sp2_snoopy_ok.png

Observed result
The taskbar remains visible erroneously
0.4.12-RC-50-geb1a43d_snoopy.png
0.4.12-RC-50-geb1a43d_snoopy.log

The bug was not recently introduced, it is known to be broken all the way down to ros 0.4.7RC1-12. I suspect the bug to be within explorer_new.