Part of the problem with certain cuts of meat, is that most of the breaking work is done in the commercial packing house, compared to the local butcher shop (almost nonexistent anymore). The big commercial shops break for mass production and sadly, many of the specialty cuts are being/have been lost.
With retail outlets (mega supermarkets) taking over, most of the meat cutting is simply stocking of pre-packaged meats (from the commercial packing house) and the re-work of unsold products (pull back). Harder and harder to find "craftsmen" in the arena anymore.
Add into that the conglomeration and confusion of the nomenclature- some for regional reasons, but most for marketing/profitability- and you have a very difficult time in explaining and acquiring exactly what you are looking for.
Since leaving the meat processing profession, I have still worked with raising, slaughtering and processing my own preferred cuts and products. Try to order a Bolar Roast, or a Fish Roast, a Pin Bone Steak, or others, and one gets laughed out of the market.
I once ordered a Steamship Round from a packer/processor that does 1000 head per day, and I was told that such an animal does no exist. After producing the NAMP manual, they proceeded to have one of their "top guys" fabricate it.......... and he came close, to say the least.
FWIW: Here is how I cut a Tri Tip: Take a beef round, (it depends on how the primals are broken: Chicago style, NY style, Diamond Cut, see here for more info: page 6) We remove the short loin on the hook and then pull the aitch bone leaving the sirloin attached to the round - remove the shank. Remove Femur bone. Remove Inside/Top Round via natural seam. Next, remove Sirloin Tip/Knuckle via natural seam. What you will have left is the Outside/Bottom Round (with Eye Round attached) on one side, and the Sirloin Hip/Rump on the other, with a tail. The "tail" is what we cut and call the Tri Tip. Cutting it from a purely sirloin primal seems to lose some of the product.