This is, of course, why the CB implements them that way. But the fact remains, the CB implementation is not RAW from any source.
The OP asked: CB inherent bonuses don't give a damage bonus from DIS, is this a bug?
I ask: there is no written precedent, so how could it be a bug?
No, DIS in CB is not consistent with CB's inherent bonuses. If you equip a +1 Magic Dagger in your offhand to fulfill the "magic implement" requirement, DIS will not give you +6 to damage, it'll give you +1, even though inherent bonuses is classified as an enhancement bonus and DIS gives you "the off-hand implement's enhancement bonus to damage rolls."
If you think the CB's inherent enhancement bonuses are working as they should, then yes, DIS not giving +6 damage with a +1 offhand implement is a bug.
If you think that CB's inherent enhancement bonuses are not RAW since they have no written precedent, then no, there is no bug.
What I am getting is I'd like to see errata so that the CB implementation of "Inherent" become the actual rule...something like "With inherent bonuses you can treat any weapon or implement you are wielding as having an enhancement bonus (based on your level)" so that it doesn't break game elements that are based on enhancement bonus. The other (less preferred) option is to reword any feat/ability/power/item so that it works with either "real" enhancement bonuses or "Inherent", but that seems like a lot more work.