Comment by account42

X11 doesn't have an exclusive fullscreen mode either. [*] It's always has relied on compositors and drivers to detect when fullscreen windows can be unredirected. Some programs chose to implement behavior like minimizing on focus loss or grabbing input that is closer to Windows's exclusive fullscreen mode but the unredirecting of the display pipeline doesn't depend on that.

[*] Well, there was an extension (can't recall the name right now) but not much used it and support was dropped at some point.