They still had clear boundaries. They slept in the sleeping place and at the sleeping time, they worked at the working place and at the working time. See, they didn't have smartphones to fiddle with in bed.
https://www.ou.org/holidays/the_thirty_nine_categories_of_sa... outlines those "clear boundaries" in detail from a pre-medieval or early medieval perspective.
> they didn't have smartphones to fiddle with in bed
This is solvable for people who want to. We have a dedicated charging station in our house for all electronic devices. Before bed, all of those devices get put there. Including me and my wife's phones.