The only issue with that reasoning is the fact if the supers are non-viable, in a sense meaning the babies when they’re neonates inside the mother, not only die, but do not form as a result of them being super. So yes, believe it is dominant, just we would need to look at it on a gene level to be sure.
Because to prove that Homo IMGs have been produced, they would have to prove their neonates out 100% IMG when paired to a non-IMG. I personally have not found a case of this yet.