OK, I said "tiling" instead of "window management", I should have been more precise but instead opted to use the same language the parent used. Coldtea claimed that the name tmux was a reference to "multiple sessions, kept open, switching between them, persisting", which I interpret as all the non-window-manager functionality — the attach/detach ability that makes tmux attractive for use on remote machines where the connection might die and you don't want to lose your processes.
"Multiple sessions, switching between them" is multiplexing. "Kept open, persisting" is orthogonal, I agree. The parent said "tiling" and I assume they were referring to, well, tiling - putting multiple non-overlapping windows on the screen at the same time by dividing up the available space.
