I waste just as much time on my phone at work that I do at home, but at home I’m able to freely seek out a distraction when I need a break, and devote my attention to it until I’ve got some motivation again, then get back to work. In the office I have to try taking a break covertly when I need one, which doesn’t lower my stress very much, and leads to me taking even longer breaks trying to regain my motivation.
As for separating work and free time, I have no issue stepping away at the end of my shift; I only work for money - I don’t give a shit about the company itself - so, as soon as I’m no longer counting the time toward my paycheck, any and all motivation to continue working immediately evaporates.
A lot of people seem to really need social interaction, which definitely seems to be the biggest reason they might not enjoy long-term work from home. I seem to be the exception to that. During the height of the pandemic even my most extroverted friends eventually started craving social interactions, but I would stock up at Costco and go literal months without ever once leaving my house, and I loved it.