What are double-cut chops?
The term "double" is not specific to pork - it's also used with lamb - but it means something different in each case.


A lamb double chop or loin double chop differs from a regular loin chop by including both the top loin and tenderloin, but not the flank. It hasn't actually been cut twice.
A pork butterfly chop is sometimes called a "double chop" because, as the name implies, it's been butterflied. A very thick cut is taken from the loin eye and then cut again to make the butterfly.


Of course, if you cut a butterflied pork chop in half, and served just one half, it would basically be a regular pork chop. So if you that's what you actually got, I'd call it a marketing gimmick.

I've never actually heard the term "double-cut chop" - there are some vague references to it on Google, but as far as I know, it's not a proper butchering term. Perhaps the term got relayed through several people and mutated somewhere along the way.