As i see it, biggest difference between senior and junior dev/manager/designer/etc. is not only amount of knowledge they memorized, but ability to hold more "key frames" of the problem in their operational memory. Not only problem they working on, but the origins and consequences of it. So more "problem blocks" you hold, the more your seniority level is, the more complicated problems you can solve. So i think it related not only to devops, but for any position. Sometimes it's better to hire a person without proper experience in particular domain, but with a sharp mind.
If you are hiring for a Devops engineer, don't hire people based on their memorization skills. Focus more on problem solving skills and how the person connects the dots for a given problem. Time is value in devops role. The faster a production issue can be solved, the better.