Is it possible he was distinguishing it from "Rodgers and Hammerstein's Cinderella"?
Did you mean "Rodgers Plus Hammerstein's Cinderella" - the official title of the recent revival, lol? :-)
The quote from the statement he released on the closure:
"Today, on this 'Freedom Day,' I have been forced to take the heart-breaking decision not to open my Cinderella."
I think it's clear, given the context and even the date he cited, that he was referring to the show he wrote. Everyone knows he wrote it. It just would have been nice had he said "our" and included everyone involved, or, honestly the pronoun wasn't even needed and he could have left it out.