I am like you, I'm someone that can happily code for eight straight hours on task and then happily jump to a side project afterwards in a totally different language / domain. Take it for the single point of data that it is, but: I have met equally as many high performers who do NOT code at home as I have mediocre ones that did. And the number of programmers who code solely on the job is far, far more common than those who take their work home with them. Statistically speaking, at least in my personal experience, that makes the at-home coder notably worse on average. As someone that used to think like you, I think the only thing you're really doing is the boys-club-esque equivalent of what the old Ivy League managers used to do (Oh, he's from MIT! That's perfect, we only hire MIT grads here). You're hiring what you know because you understand people with that background more.

You might find on the opposite end of the spectrum that someone with a perfectly equal skillset is laughing at the idea of taking on personal projects when he can just optimize for getting hired somewhere where they prioritize paying you to learn on the job.