Yes, I would think so. AS some people say, and I agree with this, to enjoy a job it has to be fulfilling. If you are an amazing compsci guy that's stuck making highschool-grade java programs, it's going to be a bit soul-sucking I'd think. Sure, you're getting paid to do simple stuff, but if I was working at google I'd hope I would get to do cutting edge algorithms and the like.

Wow look at the downvotes.

I guess I'm assuming that said PhD isn't doing nothing but unit tests all data, but rather writing unit tests for their code.

Good unit tests are hard, often harder than product code. Smarts and experience help.

Assuming the PhD was not in something related to software testing and is not entirely worthless, you're either overpaying for irrelevant skills or paying someone less than they could get elsewhere. Neither are a good thing.

Not in itself, no. I'd be happy to have a PhD writing unit tests for me, but if they're overqualified for that (which I think is the assumption we're making) I'd probably rather have them working on a harder problem.

I think the point is that it's not an efficient use of their skills.