Untrue in my experience.

Games still can render more FPS than mandated by vsync.

I tried playing sauerbraten (with SDL2) on sway other day, it was butter smooth (no tearing) with vsync off in game, and I felt no input lag unlike when I switch vsync flag on in game which limits FPS.

It probably does triple buffering, but somehow on sway it worked better than triple buffering of intel's xorg driver back when I tried that.