Do you mean both simulated software fullscreen and exclusive fullscreen mode do not work?
Yes, and no. Exclusive fullscreen mode kinda f**ks up Gnome Shell if you don't close it just right, so that is annoying, but I am talking about the 'simulated software fullscreen' where you just create a frame, make it fill the window, and undecorate it. If you try to set it to always be on top, the Gnome Shell top panel sometimes still shows above it, and no matter what you do the bottom right hot spot can still be activated, which sucks, but at least the top right deactivates!
I found the if you request focus right before you maximize the frame it will display over the top panel.