There are two fallacies in your analogy.

Segfaults are precise symptoms - they occur only when there's a memory issue. Autism isn't precise, is a collection of characteristics that manifest differently in each person.

Genetic is, for the purpose of this conversation, a precise diagnosis - means you carry parent genes that will cause the issue. Memory management isn't: what caused it? Code error? OS error? Processor? Is it a bad code path or a unexpected exrtenal state?

Finally, an analogy of your analogy: you measure someone temperature and it's 40C. You diagnose a fever.

Segfaults are fever, just a symptom.