I don't think it's fair to characterize such people as "incapable of learning how to do new things" if they're not even being given the opportunity to learn.

I'm not saying that the OP should hire these people, or that they would even be good hires. Maybe they don't want to take the risk or time of training up a new employee.

It just seems like a bit wierd non-sequitur to draw conclusions on someone's learning capabilities based on their performance in an interview outside their usual domain.