Well to be fair ALW himself makes no pretense that he was the first to do a Phantom musical.
I do think Yeston's weakness is lyrics--and for some reason I have more and more probs with his lyrics as he progresses (I love most of Nine--I think Phantom has some almost laughable lyrics as does Titanic though not always as much to do with rhymes as to do with character--ie Titanic how we have big rants liek the telegraph guy going on about the history of the telegraph, the chorus singing about the building of the ship, stuff I don't really see their characters doing).
I like ALW's Phantom but as a guilty pleasure (and one I don't dive into very often) but as much as I think Yeston is pretty up and down as a lyricist I don't think anyone can defend Hart and (especially) Stillgoe's... (I felt a tinge of pity for Hart when I read on Wikipedia his quote about wanting to be the British Sondheim

)
Cats--wow I actually agree with you on something--ALW owes a lot of his success to the vision of his production--thanks to Bjornson and Prince and how iconic that look for Phantom became. From what I've seen and reviews I've read none of the productions of Phantom by Yeston had anything as visually comparable (and I don't mean elaborate wise--I mean striking--where was tommy Tune?).
So I assume that nothing from Yeston's Cage was recorded?