I understand that they found strong enough evidence that it's a genetic condition, but at the same time it's not one single gene, it's a combination of many that combine to create the full spectrum, hence no easy genetic test. They'll get there in time as technology and research evolve. I don't see any circular reasoning.

EDIT: they have a FAQ about it: https://www.autism.org.uk/advice-and-guidance/about-autism/w...