Sirloin… So we’re looking at the rear section of the pork loin. Modern pork is bred to be finely grained and dense with little or no fat in the muscle bulk. Chalk it up to people having a fear of fat for the last 40 odd years. OK, that’s my little pork whinge over with. 
I really haven’t done much with loin for years because it can have a tendency to be dense and dry. I haven’t even revisited it since starting to play with sous vide. The last thing I did with pork loin was to bone it out, roll it and cure it as ham.
It’s also worth noting our pork tends to get portioned out a little differently to yours, as well as being labelled differently.
I go for the other end when I want pan seared porky goodness on my plate and a pork scotch fillet ‘steak’ rather than the classic chops these days. I find the flavour is much better and worth the slightly higher price.