The official time that each sport gives is different everywhere (and even different amongst different ruling bodies in the same sport). Really all that is though is an indication on how seriously the ruling body of each sport takes the injury, not what is best for the player.
I'm very surprised that football is still only 6 days. Can pretty much guarantee that will be increased up to two weeks within the next 5-10 years, as I expect most sports will do.
A lot of people don't seem to take concussion very seriously. Some of the comments on the Karius thing a few months back really showed that some people don't understand what it is. It is literally a brain injury. Which is bad enough in it's own right, but coming back too early and opening yourself up to the possibility of suffering another one on top of it is devastating. Far worse for the player than pretty much any other injury. As much as I want Shaw back as soon as possible, I really hope he's not rushed back too fast. It's simply not worth it.