It's not in fact that impressive. The math for all sorts of cryptography goes over Schneier's head (as he sort of infamously implied with elliptic curve, over a decade ago). That's normal! Cryptographers specialize. Having a really careful, fine-grained, up-to-date intuition for differential cryptanalysis is crucial for designing hashes and ciphers, but less so for a key exchange.

Not writing this to dunk on Schneier so much as to relate that cryptography is specialized, and that generally there aren't a lot of people that you'd expect to be ultra up on PQ key exchanges and modern block cryptography.