IIRC, Gillian Lynne tweaked the choreography in Masquerade and somewhere else. I'm not aware of any other changes, although somewhere in the 2010s Hal did a complete refresh, with new paint, costumes and full company rehearsal. I think people involved have stated he regularly visited and gave notes.
At my last pre-pandemic semiannual trek to Mecca I told my traveling theater buddy I wanted to see Phantom on Broadway and his pearl clutch would squeezed oil from the desert. I had seen many tours, but have never seen it on Broadway so it was added to "The List." I agree with PurpleMonkey. See it at The Majestic if you have a chance. It is still magic.
