Self fertile mutations of a species that is normally self infertile are pretty rare, but it can happen. More likely is another scenario similar to this:
Holly plants are male or female, and you must have both for pollination if you want berries on the female plant. There is a "type" of holly marketed as self fertile: Merry Berry is the name, I think. But actually, what they did is plant a female plant and a small male plant in the same pot, so the buyer thinks he is getting berries from one plant, when in fact it is two (a male and a female).
I can't really say if this is true, but planting two different honeyberries in the same pot as one plant is the most probable way to achieve the "self pollination" that is advertised.