It's possible to be a "wordpress programmer" in any language, but man, I have read a lifetime's worth of bad PHP code. WordPress is of course the worst of all possible PHP worlds since it was a fork of an even more ancient project and thus had to maintain backwards compatibility with a purely procedural codebase.
The phrase "wordpress programmer" conjures up the person for whom that is their sole form of programming expression. Some part of me acknowledges that people like that must exist: the rest recoils in horror.