Yeah. There is something about carving out the image of your own mind and getting absorbed deep inside it. I will write from scratch much more than I need if it strikes me, break whatever rule I want, give names that only make sense to me. It is a sanctuary
You can tell my engagement level with my job by the commit frequency on my side-project.
If I'm deeply engaged at work, I don't have many spare cycles out of hours and there's little happening - library updates and small fiddling.
Otherwise - it's full steam ahead on projects that I somehow magically find the time for.
I don't work on my stuff during work hours - disengagement from work results in more energy and motivation to do stuff out of hours.
Weirdly, I think this actually benefits those boring workplaces too. If I'm scratching the itch with what I'm doing on my side-project - it means I'm less likely to invent interesting new ways to over-complicate things at work.