That humans who have grown out of their optimal brain plasticity and hence never acquire the capacity for ordinary human language are not somehow "conscious" is

That humans who have grown out of their optimal brain plasticity and hence never acquire the capacity for ordinary human language are not somehow "conscious" is not supported. Rather, it means that, by its very definition, we do not have the means to communicate with them in order to even ask the sorts of questions necessary to determine such a thing. The premise is unfalsifiable.