I'm using academic writing projects here as a proxy for what Newport calls "deep work" and relying primarily on the work of Robert Boice, but also on studies of non-academic writing, as well as the experiences of successful writers such as Stephen King.Good results depend on many variables. One of them is the intensity level of distractions. Another one is the duration of time without distractions. The probability of good results is inversely proportional to the intensity of distractions and directly proportional to the duration of time without distractions. Cal Newport suggests that by blocking time for deep work we extend the available time without any distractions. It seems to be more distraction prooof than "writing regularly in the morning" and hoping that nobody will knock on the door.
There are many examples of successful writers who wrote under terrible conditions, in bits of time snatched from other responsibilities. It also appears to be true that time spent writing is not so important. What appears to matter most is the commitment to write regularly.
There is also good evidence that dedicating large blocks of time to writing is not particularly helpful. Binge writing plans, where large blocks of time are allocated over a relatively short period, is no better than no plan at all. There is also very good evidence that many would-be writers use lack of large blocks of time and environmental distractions as excuses for procrastination.
I have seen many students suffer from the "I need to be at my favorite coffee shop table with my favorite headphones on" syndrome as a form of procrastination. I also think that scheduling big blocks of time for "deep work" is a bit like starting a meeting off with "Who's got a really good idea?" I think it is fine to schedule time for important work if i know what I am going to do. If I don't know, I'm probably better off taking a walk. But YMMV.