This is possibly the best description of my development process I’ve ever seen.

I’d add “staring into the distance” alongside the mumbles (yes, when pacing, that often means I run into corners of walls, couches, etc).

I think of it as iterative development in my head, and it’s often focused on finding the fastest path to proving that an architecture or implementation is wrong; when I find it hard to prove why something won’t work, then I begin to explore in depth the idea and have a pretty big running start on the code, which flows a lot more quickly when I’ve done this than when I just sit down and start typing.