Is it though? The way I see it it saves me a lot of time which means I can end my day earlier.
Plus, a socializing lunch break in the middle of a day cuts your space for deep work in half, which means you'll often not get any done in either half. That's why I always brought my own lunch and/or ordered stuff to the office to eat at my desk, and went with people to lunch only every now and then.
How productive is 8 to 13 hours of deep work? Personally I need a break every so often to celebrate the incremental wins, else life becomes one long problem to solve.
8-13 hours of deep work are unsustainable on most jobs. My problem with breaking day in half is that deep work tends to require some runway; 3.5 hours is not much if you account for the time it takes to achieve full concentration.
To me it seems like it is the companies that have "cool" offices with ping pong tables that try to get you to work 13 hours instead of 8