I am looking at a FRA-BCN ticket on Vueling, who clearly can make the route happen with a connection in MAD (see picture, which I generated by doing a multiple destinations search). However, when I try to book it as a single route by starting with FRA in the search box, my only destination option is MAD. Will they really not sell multi-segment flights? (This is my first time booking a budget European airline, so forgive my ignorance...perhaps this is a known thing.)