When I started 6 years ago, it was all Emparedado. It is falling into less and less use although you can see it on a menu every now and then.
Personally, I've only seen it once on a menu in México. I am glad they replaced it with sándwich here in Duolingo even though Sándwich is a term that is borrowed from English. It is now even in the Royal Spanish Academy (la RAE) dictionary: