Final answer:
The venison loin cut that remains attached to the backbone is called a saddle. It is distinct from sirloin and tenderloin cuts, which are not attached to the backbone. The rack refers to rib bones attached to the meat, not the loin with the backbone.
Step-by-step explanation:
When the venison loin is left attached to the backbone, the cut is known as a saddle. This includes both sides of the loin, with the backbone in between, and it often results in a larger, impressive cut that is suitable for roasting.
In contrast, sirloin refers to a different part of the loin, and tenderloin is a specific, highly tender muscle that runs along a portion of the spine, but is not attached to the backbone. The rack, generally refers to a section of rib bones attached to the meat, more commonly associated with cuts of lamb or pork.