In Elements - Access - Details View, there's a tooltip that tells you the field can be affected by another field (Views Access level in this case). It might be good to have one for the Form label setting that mentioned this--if the Form Label view had had a tool tip that listed the possible effect of the Group Label setting (and vice-a-versa I guess) it would avoid the issue of idiot users like me turning it off when testing for something else.
I was stupid to have changed it at some point and not set it back, but in my defense the various menus have an awful habit of jumping back to the first setting tab when clicking SAVE, which, (especially to a new user testing to see what things do or desperately trying multiple things to solve a problem), can sometimes make it hard to find your way back to return a setting you just changed with no obvious ill effect to it's original state.