absolutely, but are monolingual quechua speakers immigrating to Spain? Portugal has the same sort of arrangement with Brazil, but I have never met any indigenous Amazonians making use of it.
I'm not saying it's a bad thing at all, I'm for a more open migration policy, but I wonder if it's the whole story. It's one thing to welcome Spanish speaking migrants from elsewhere, another to just open the border for whoever. I doubt Spain does the latter.