When I hear "web developer" I think of a person who produces web applications. "Web designer" is the term for someone who produces WordPress sites.
Less important than whether or not he is "junior", he needs to know what to call himself in order to correctly communicate the value proposition he's offering to the potential employer's HR department. The only way to know that is to figure out what people call what he wants to do in his market.
Maybe he's a "web developer", maybe he's a "software engineer", maybe he's something in between. But he should definitely A/B test terms to see whether his responses change and how.
For instance, my title for a web marketing agency was 'associate software engineer'. It was the typical job of setting up CMS sites, customizing plugins for them, or occasionally making a very static site from scratch.
I gradually got into doing more complex work like writing apps on MVC frameworks. But I think there may be indeed another career ladder I need to jump on if I want to actually do the "engineering" part correctly.