female protective effect...

From a quick look it seems like a stretch of an idea back when there was little recognition why it seemed more prevalent with males. 

What has been proven is that females are more likely to be aware of how others perceive them or more likely to pretend to fit in so as to not experience social exclusion. This is somewhat important for all females as there is safety in numbers add the evolutionary need to find a partner and ensure they help support the children.

Suppose we classify a 'Trait' as an external behaviour. If Autism is understood (as it is becoming to be) as just a different way of our brain using it's compartments somewhat differently (different oscillations, different networking, using different lobes) to process and reason and understand the world, then the external behaviours aren't a symptom but an effect of how and what we're experiencing. And if I'm keenly aware that repetitive movements to feel grounded (stimming, if you like) are always met with negative responses or aware that my questions are left unanswered or worse, treated with contempt, as a female (which I am) I may withhold external behaviours that 'appear' autistic and just go silent, as most my age did in the 80s, 90s and into the Naughts.

I have a friend who's in genetic research and essentially has found proof we ALL have the same genes which can be switch on or off. Nothing mutated, nothing odd, just like a light switch - up or down. There is so much that goes into who we are starting with the the brain, add ones environment, add socially acceptable behaviours and 'codes' add how my biology responds to the environment or the food I fuel it with. 

'Protective Effect' is a weak argument as far as I can tell. Protection from what? I love every part of me. They could've chosen a different word but the appeal is to Neurotypical individuals who have trouble relating and understanding how an Autistic engages with the world.