I wouldn't say that it felt like I was thinking really hard in times I wasn't writing. It's a bit like the technique of putting down a crossword for a little while when you get stuck - you might not be thinking much about the puzzle, but somehow you're turning it over in your head.

FWIW, I do agree with the original comment at the top of this thread that this technique couldn't yield 48 books in 2 years - there's only so much headspace available, and this technique is one that taps into that headspace effectively for long-term projects, but it's not magic.