> he didn't even know how to open a terminal and SSH into the box!
You just described something which is trivial to learn in less than one minute. This lack of experience does not directly speak to their skills or abilities.
Extending your example to illustrate its irrelevance, were I to have spent 60 seconds with this engineer alone just before your little ssh test, he would still appear to be a 10x engineer to you.
Focus more on ability and less on what one has or hasn't seen just yet in their careers. I could easily find the limits to your knowledge in seconds and I'm quite sure you could return the favor. I'd gladly hire someone who demonstrates the ability to become a wizard in X and not care in the slightest if they've seen Y and Z yet. I can teach Y and Z to someone like that very easily.