That is because the signal that college is supposed to provide has also been devalued to an extreme degree. It's simple - a bachelor's degree will soon be the equivalent of a high school diploma.

That is why for a lot of roles a motivated, smart high-school dropout is a better hire than a college student.

I don’t know what you hired them for, but if it was a skilled labor task they had some sort of signal in their resume they could do the job (github repo). We are talking about basically taking HS graduates with nothing except grades/extra curriculars and investing N months in training them for some job you have no certainty they will be able to do, and no assurance they won’t just go to your competition afterward.

That's because your interview process is already biasing the result. To get a fairer comparison you should take a random sample from both groups (out of all the applicants) and see (although self selection bias is still in play here).