just installed 12.6.1 on MacOS El Capitan 10.11.6, upgraded from 12.5.2. Full Screen mode no longer works. I click the green button, and it just (vaguely) Maximizes the window, instead of entering Full Screen.
This makes Pro Tools break the standard of MacOS since at least Mountain Lion, and is a severe hindrance to usability on small screens like a laptop. The standard for MacOS is that clicking the green button enters Full Screen (i.e hidden titlebar & menubar, and window fills whole screen), and option-clicking the green button maximizes the window (keeping the titlebar & menubar visible). So if you follow the standard, everyone can have the behavior they want.
12.5.2 (and before, at least since 12.3 i think) worked fine in this regard.
EDIT: still broken in 12.7 on macOS 10.12.2 😞