So I literally just learned about this, and it's because it is 3 buffers. I found this website to be a good high level overview: https://wiki.c2.com/?TripleBuffer

If that's not short enough the tl;dr is: "with Triple Buffering, there will always be a buffer to write to while a transition is in progress between the other two." The other two buffer's being producer, and consumer buffers.