[@Dedonus][@Dedonus][@fdeviant] Well I'll voice my thoughts even though I should be working. Meta Humans might be a blanket term but it shouldn't be used as such. Everyone gets their powers from something so there will be genetic strains which have nothing in common. For example.

Hydro and Arachne. Both are Meta Humans. But the cure for the Meta Bomb should only work on one of them. Since Hydro mutated from another source.

Metas are made and could still have residual DNA of their Human selves. Unlike Mutants who were born and have long discarded any old DNA. I admit I have no idea how DNA works in Real Life but this isn't a Real Life Science. Not when powers are involved. For the sake of clarifying things let's say that the Meta Bomb and it's cure doesn't work on Mutants or those who have been Metas for some years now. 

Because they no longer possess the DNA of their old normal selves and have permanently become something more. While those recently changed have a timer before their change is permanent. This is just my thoughts on the matter and might explain why those with powers won't be affected by the Meta Bombs since they are no longer strictly Human.