I mean it is also the case that as a dev I spend a lot of time thinking about stuff, but in a way where I can sort of be doing something else at the same time. Often doing something else at the same time helps because if I'm not I get bored and stop doing it altogether.

So I'm goofing off on HN while background processing the design of a thing. Sure I could be staring at an IDE window when doing it, but instead I just open it to check things when needed.

I'm sure I'm less productive per minute than if it is all I was thinking about but I'm more productive on the scale of a full day if I am only half focusing on certain things. I have ADHD though so I'm probably not typical, but my point is that for intellectual work just because you can't see it doesn't mean it isn't happening