Selecting change crosshairs icon (left tool bar) does change the icons background to light blue, indicating that it has been selected, however - the crosshairs do not change to full screen crosshairs. Additionally- selecting "full screen crosshairs " from the pull down menu does not produce full screen crosshairs, but the menu item does have a check mark indicating that it has been selected.
KiCad 5.0.1 - MacOS 10.14