[Zamicol]

All the works I've read of Schneier have given me the impression of the above definition, "support multiple cryptographic primitives and do not be overly coupled to a single primitive."

Serendipitously, I just tweeted about this 11 days ago: https://twitter.com/CyphrMe/status/1556660870901403648

"The moral is the need for cryptographic agility. It’s not enough to implement a single standard; it’s vital that our systems be able to easily swap in new algorithms when required."

Do you have a link to something that in your mind represents what Schneier is talking about?

[tptacek]

A modern cryptosystem wouldn't be designed to swap in new algorithms; it would pick a single set of algorithms and constructions, and version the whole system. Which is how WireGuard works: you can't run AES WireGuard, or WireGuard with the standard P-curves.