Whole boneless loin has the boneless rib end, boneless center cut, and boneless loin end roasts as 1 piece and continuous, usually minus the tenderloin.
"Boneless Roast" can be any of the three or a combination (rib end including some center cut, or loin end including some center cut). In other words, a partial whole boneless loin, and you always pay more for part instead of whole.
These have become more popular as the company has increased tenderloin merchandising; i.e. in-package marination varieties of flavored tenderloins. So, manufacturers merchandise more heavily of the rest, including boning out the whole loin and selling it as such, whole or half, plus riblets cut off the end before boning, and pork bones, baby backs, smoked neck bones (actually from the loin end, not neck, but most everyone wouldn't know the difference), etc etc. The more you merchandise the more profit is made. You can sell off the loin meat boneless at a low price and make a high profit on the parts and pieces, garnering excess overall yield from a whole loin.