When installing GNOME3 I had a little chicken-and-egg-problem. Without installing additional drivers GNOME3 wouldn't work, so the fallback mode was handy to search the internet for the correct drivers for my chipset and install them.

But as long as they have some solution for this problem (and I think it is pretty common, because debian always installs with generic drivers for your hardware), I think it is no problem to remove the fallback mode.