It doesn't force applications to be fullscreen, but it does have garbage tooling for managing multiple windows on the screen simultaneously. Even windows has better with hotkeys and gestures for snapping to parts of the screen.
Mac OS originally didn’t have the concept of full screen (expect for games, pro software) or tiling. Its floating, overlapping and spatially oriented windows blew people's minds. It was coherent and wonderfully executed, both powerful and simple, I miss it dearly.
During the OS X brain transplant and particularly after Lion it became a hybrid that’s neither here or there, unfortunately.