But it may contribute to you getting an interview in the first place, no?
A few years ago I was offered a job explicitly because I had a github account where I hosted a public project that used a framework.
Later, I was the recruiter in a few hiring rounds, and public source code repos was my primary source of data to assess q candidate. If a candidate had shit code in their repos, they'd be rejected. By "shit code" I mean a candidate for a senior software engineer for a C++ project showed up his GitHub project as his C++ portfolio, and all he had for show was a project that didn't even used include guards.
It was a bundle of declarations that included duplicate definitions on each source file. The candialdate then expected stuff to remain consistent by updating all declarations.
If you intentionally put up your GitHub page in your resume and all you have is "incomplete and unpolished exploratory projects", that's how you're choosing to present yourself.
Also, the degree of "unpolished ness" actually attests to the skillet you bring to the table. If the "exploratory projects" you choose to showcase as your portfolio are ungodly messes, you should not be surprised they reflect poorly on you.
> It's surprising that you would take pride in using this as a basis to disqualify.
I know for a fact that public GitHub repositories explicitly presented by candidates as their technical portfolio is an accurate reflection of their skillet. I am certain of this fact because I never used personal source code repos to exclude candidates but to guide the interview, and each and every single candidate I interviewed that published crap in their portfolio was lacking absolute basic competencies in the domain they showcased.
Do you have any data to refute this?
Of course, it might happen that they'd hire contributors, as you say. I'd say this is incredibly rare (but does happen). Usually, from my experience, this happens when the company wants to essentially "acquire" the code (and sometimes, the contributor is hired as a contractor for a couple months).