I think the point was they dont like low levels in the same WarZones and high levels, as the high levels pretty much just stomp them usually.
OP, they did that to get things up and running. By adding everyone and normalizing the levels the best they could, they made it possible to actually use WarZones on day one. If they bracketed everything from the get go, you would have seen que times measured in HOURS for WarZones, not minutes.
Eventyally as people spread out and level, we will see more and more brackets added, the first of which was in 1.1 with the lvl 50 bracket locking lvl 50's out of low level WarZones.
Patience, Rome wasnt built in a day.