Yes, this is correct, genetic inheritance does have a strong correlation with the incidence of diagnosis of ASD.
There are many other factors that may contribute as well, and its a good thing to see so much research taking place concerning the causes of Autism.
It would be great to give people with Autism an answer as to what caused their condition, and it would be particularly good for parents of Autistic children to have answers. Unfortunately the studies that have been performed show no conclusive cause of ASD, even though there are people that will latch on to various ideas, (although some have been disproven, like the theory that vaccines cause Autism), because of a deep seated need to understand what has happened to them or their children. This is human nature, and totally understandable, if you have worked with parents of Autistic children you see this a lot.
Others latch on to these various ideas, particularly the disproven theory of vaccines causing Autism, because of their own particular agenda, even though they have little or no understanding of ASD at all, this can be seen very clearly from some of the posters here on this forum, as well as CZ as a whole. They are however entitled to believe whatever they choose.