I think I'd want the smarter candidate regardless in a job like software development that is overwhelmingly based on quiet focus time. It's easier to help them work through the rare emergency, than to help a less-skilled employee work through literally everything else.

But just blanking when suddenly put on the spot happens to everyone. Human memory retrieval is a complicated process, nothing like a computer. You can have vast expertise in there but not be able to retrieve it instantly, unless of course you've practiced interviewing that very subject a lot recently.