What you are describing would've taken days, whereas I got him squared away in an hour. I know because he'd already been stuck on it for days, with him asking the occasional question in person and via chat. It wasn't until we sat down together and went through the process of how to make these kinds of modifications step-by-step that he really got it.

We don't have guides for how to make every different potential change to the code. That'd take more time to write than I currently spend coding, and they'd constantly be getting out of date with every refactoring. And anyway, the change I was walking him through was a refactoring of a kind we hadn't yet done before, so no guide would've existed anyway (and, if written, would likely be a one-off). I'm not spending hours writing a speculative guide on how to make that change, which I couldn't even write properly without actually making that change, when it takes much less total time just to sit down with him and work through it together.

I don't understand what programming world you are talking about, because it's completely different from my own. My experience has been that collaborative, high latency development mentorship via email tends to take an order of magnitude more walltime than sitting down and writing the code together end-to-end (similar to "extreme programming", but for mentoring).