Maybe this live introduction by Phil is the source for this spelling?
That's great!
Of course, that does introduce a possibility that could actually be the explanation for why it is spelled that way in the credits, i.e., it could be a nod to the fact that Phil and/or others have (intentionally or unintentionally) mispronounced his name so often over the years that it felt right to spell his name bizarrely in the credits in what could be the band's final official video release. An "in-joke", as it were.
After noticing the misspelling, I did analyze the end credits more closely. It appears to be the only misspelling in them. So, I guess we have two possibilities: an incompetent typist or an inside joke. I wonder if there is any way to find out for sure...