[EXPLORER] DosBox 0.74.2 leaves the taskbar visible when switching into fullscreen via Alt+Enter

I double checked earlier, this issue affects only explorer_new, but explorer_old was not affected for DosBox

This issue is very old already, and I am pretty sure that it's broken in explorer_new.
VBox 4.3.12, VBEMP, desktop resolution 800x600 32bpp

Expected result
When pressing Alt+Enter in DosBox 0.74.2 we expect the taskbar to be hidden, like it is in WinXPSP3

Observed result
The taskbar will remain visible when switching into fullscreen
0.4.12-RC-39-g27da885__dosbox0_74_2.png
0.4.12-RC-39-g27da885__dosbox0_74_2.log