It's worth remembering that not everything in a song is about this-then-that narrative. Taken to an absurd conclusion, one could object to choruses for the same reason.

There's plenty of other things that don't make sense from a literal storytelling point of view in folk songs. So many songs shift from third-person narrative to first-person narrative without any reason or explanation. "He" or "she" or "this fair maid" or "this lord" abruptly becomes "I".

Nobody objects to flashback in a movie; that's effectively what a last-verse-repetition is for song.