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:
Interesting. It used to be that way in Spanish from English course until, say, 2018. I am not sure when they did change it.
They probably modelled Spanish from German course based on original Spanish from English course but never got around to update it.
That said, while I was doing some mixed strengthening practice I came across with emparedado again (in 2020) but because it was already in my database words learned. Newer users might not ever get exposed to that word in Spanish from English course.