It isn't designed from the top down. That is, yes, the RNC (in concert with the DNC) blessed IA/NH/NV/SC as the chosen four, but everything after that was left to individual state legislatures to decide.
They could easily have made up some excuse of "respecting the rights of the early states" to impose delegate penalties on these states for going early. Or subtly encouraged the establishment friendly states to also go in the beginning of March to create a 2008-style Super Tuesday.
Well, there are delegate penalties for going early. The penalty is that you can't use WTA delegate allocation. If it does turn out that this race is a Democrats 2008-esque delegate maximizing marathon rather than a momentum race, then the later states will have disproportionate power.
[Yes, as I've said before, there are only something like 7 or 8 states that are statewide WTA, but the later states are also more likely to be WTA by congressional district. California, for example, is WTA by congressional district, plus an additional share of delegates that are WTA for the statewide winner.]