Just one thing to add to this: there are two different things which are generally called "triple buffering". The first is more accurately defined as adding a buffer to the renderqueue this always introduces additional latency, and is what most DirectX games do when you enable "triple buffering". The other, actual triple buffering, adds a third buffer so that there is always one available to render into, but always continues to render and always displays the most recent frame. This is what happens with desktop composition and borderless fullscreen.
Yeah, it's annoying that to communicate on this topic you have to use the term triple-buffering, when you're usually talking about a render queue.
I didn't know that desktop composition implemented true triple-buffering. That's interesting.