So I normally play on fullscreen, but I've been playing fullscreen windowed (not borderless, I wish that was an option - for discord overlay reasons)
The things that I've noticed.
Launching the game, when you maximize it while loading, it'll revert to unmaximized after loading to the main screen.
Maximize again, loadinto a character, unmaximized (edit - not the case anymore (maybe ever?) - edit AGAIN - It does happen, just not when loading into a character. It's when you laod into the character select screen)
Maximize again, zoom into first person, unmaximized
A bit of a weird issue, not really all that impactful, but its a bit odd to tsay the least.