How is the heritage not an all mt board? Sl is one step above their softest park board and the f1, raptor, and summit are all more true freeriding/alpine boards than the heritage...
How many people would regularly take a Heritage to the park? Not many - or not nearly as many as would take an SL freeriding. Hence, SL is more of an all-mountain board than the Heritage. Now, I would still consider the Heritage pretty much an all-mountain board, but certainly less so than the SL.
Incidentally, FWIW NS only labels the Cobra, SL/Legacy, and Proto as all-mountain.
BTW, SL is 2 steps above the softest park board (Proto is 1 step up).