I think the intended implication is that Wiles has not read or understood all of the proofs he built on. If someone said, "nobody dead or alive understands all

I think the intended implication is that Wiles has not read or understood all of the proofs he built on. If someone said, "nobody dead or alive understands all the details of Windows" I doubt anyone here would find it controversial. It's too big to fit in one person's head.