I find that difficult to believe. Estrogen isn't known to cause large behavioral changes like you've described. The changes in hormones can result in some emotional changes, but I cannot see how they would reduce symptoms of autism.
But there are plenty of symptoms of ASD that have nothing to do with stereotypical gendered behavior. And they are a requirement for diagnosis.
Personally I don't know.
People who are gender-nonconforming and/or trans, are more likely to have the main trigger event for being diagnosed with autism: being told that they seem autistic. Which will lead to more of them "being" autistic (in the medical-statistics sense, under which people who have ASD but are never diagnosed, get categorized as "neurotypical.")
I'm not saying I necessarily believe it, but it's one of the most interesting articles I've read recently.