Automatically award PIP to those with a lifelong disability that had a DLA award

I believe the PIP assessment is wrong as it should not be a one size fits all - just because someone can cut up & cook a bit of chicken doesn't mean that they don't struggle in other areas of their life. My son is on the autistic spectrum and his DLA was awarded on an indefinite basis as his disability will affect him for life but when he had a PIP interview they decided he was ok. It is wrong that he and countless others have got to keep fighting for their rights when life is hard enough as it is. Perhaps more time should be spent on investigating those who are falsely playing the system.