This isn't a great article, but for Box Breathing and many other zero-risk wellness activities: Just try it. There's huge variation between people, so obsessing over the impact on the average person will take more energy than getting concrete data on how well it works for you over the course of a week.
FWIW it's been a small but positive addition to my stress reducing toolbag. Best of luck.
Because a natural thing is to breath regularly in and out in the same pace stabilising pulse variability, not forcing 4 arbitrary phases disrupting natural cycle.
I think that for a deeper syncing even better is to try to follow these intuitive tops and bottoms - it's like prolonging breath and filling a specific sensation. But it's more for relaxation as breath becomes slower & longer then nearly using only stomach/diaphragm.
FWIW it's been a small but positive addition to my stress reducing toolbag. Best of luck.