Aside from the "gum stain" variation, they pay homage to printing errors of the past like "green tints," "photo variations," "Milton Bradley backs," etc in the Heritage series of cards. When they remade the 1962 set, they added a Jackie Robinson series for the cards where Babe Ruth was featured in the real Topps set.
Think of the gum stain cards like a colored refractor, because it's a base card parallel made in limited numbers.
https://www.comc.com/Cards,sr,i100,=gum+heritage+2015