Lightroom: LR4 dual screen, actions applies on all selection or just one depending on what screen has grid view

Very simple to reproduce.

In grid view (main screen):

– Select a couple of photo (2 or more)
– Let's move theses to quick collection by pressing letter « B »
– all of your selection is in quick collection. press « B » again to remove them.

Switch the grid to the second monitor (by pressing « SHIFT+G »):

– do the same operation, but now press « B » apply only on one photo.

This is do the same with quick collection, stars, color, mark...