It's a bit glib to say that even the most leetcode interviews "require memorization". It's certainly possible to do most of them from "memorized" first principles of how various bits of CS components work instead of brute-force memorizing, and in general even when I do code problems on interviews, I mostly try to use them to either demonstrate that or determine that the candidate actually understands WHY you would do things that way.
Certs on the other hand are often just pure memorization. There's not really any way to "infer" which AWS service name matches to which service function. You either know the name of the API call or you don't. It doesn't provide much signal that you actually know how to apply that information to anything practical.
Even at their worst, most crappy whiteboard code interviews are still literally testing if you can literally write functional code, which is closer to what you do on the job than memorizing the Cisco books.