There used to be 2 signals for pedestrians -- walk and don't walk.  That was clear.

It's the introduction of the flashing hand signal that confused matters.  The solid red hand means don't walk, so we don't need another signal that also means don't walk.

And I agree that the underlying reason people are walking on the flashing hand signal is that it's not safe or reasonable to give pedestrians only 5 seconds to legally enter the crosswalk.  If a turning car is blocking your way when the walk signal is on, do they expect pedestrians will wait 3 or 4 minutes for the next cycle to have another shot at it?  Not freaking likely.