Tried to login earlier, but kept getting an error message that I was trying to connect to the wrong url
What he has there is technically the Sirloin Cap.
The Tri-tip, part of the Bottom Sirloin, starts in the Sirloin Tip (part of the Round), stretches over the top of the Sirloin (hip) and ends up just a short ways over the Loin. Some packers strip the Tri-Tip, Ball-Tip and Flap Meat before the Hind Quarter is broken down.
However, if none of the muscles are pulled, and the Hip is separated from the from the Loin, the partial Tri-Tip muscle is the Sirloin Cap.
I hope this makes sense to you?