In the UK, at least, it seemed to depend on several decades of accumulated rules and whatnots that only the PRS understood[1] (but I haven't been involved in anything related to music licensing for a few years and even then it was baffling.)
[1] Things like "was it on the radio or a TV show or a live performance or a recording? who was the composer? which licensing region was it in?" etc.
[1] Things like "was it on the radio or a TV show or a live performance or a recording? who was the composer? which licensing region was it in?" etc.