Yes, but now you've shifted the goalposts, because I think most people would generally consider PL researchers to have an understanding of programming language design.

Well, that's fine, then. Many of them do eventually create something useful later.

Johnathan Blow is a game designer, though.

You can be more than one single thing. Johnathan Blow is a game designer, a game programmer, an entrepreneur, a programming language designer, etc.

At the end of the day he's someone who do write software for a living since decades, and has strong opinions and expectations. And he's using this to create the tools he wants to have.