points jersey hadn't yet fully morphed into the best sprinter's jersey. the point system still rewarded placing consistency throughout the race. Not so tilted to flat stages, etc...
sagan found his own version of the old system by getting over one mountain in order to collect the sprint points to make up for the fact that he might not rival the pure sprinters.
i kind of wish it returned a bit to the more even system where it might reward a rider with Kelly's qualities. WvA would likely be a shoo-in, but who more deserving than a rider who can place in a sprint, a TT, and a mountain stage?
it depends on what you want to reward, i suppose. however, the history of the green jersey is not specifically the best "pure sprinter".
Good chance Pog wins all four jerseys.