The explanation that RC gave was pretty straight forward.
Think about it this way, what product stays the same for an extended period of time? Not that many. Everyone is always changing, everyone is always coming up with newer and better things. The new injectors likely won't be out for another 4-6 months and from what we have been told so far, a bit higher price tag. They will still be the same size, the same design, but they said the spray pattern will be better. IMO, not a good enough reason to skip out on a group buy that will save you hundreds