I don't know. I have spent most of my adult life ignoring Phantom. What I DO know is that the opera is dated 1910, that the musical is dated 1986, and that in 1986 the duration of a copyright was 70 years. So either he settled for no reason, or their was new material added to the opera at a later date. I was just going on the math so if there is more here I plead ignorant.