Nah, as a writer who talks to other writers with wildly different processes, I don't think that's how it works for anyone. Time spent writing is almost unrelated to visible time markers in the text. It's not a big deal to stop writing in the middle of a scene or stop one and start another in the same session (assuming we're writing linearly at all). Scene and chapter boundaries are something we specifically think about in their own right to optimize the reading experience.

True. Personally when I write I do like to always start the next chapter or whatever is the "unit" or "task". But then stop. The units for the writer are probnably not the same as for the reader. But they serve the same purpose, taking a break, letting you think a bit about what was done and what will be done next.

There is a rhythm. We live one day at a time. We tell one story at a time. We post one HN post at a time. :-)