The gender disparity in autism prevalence is one of the big mysteries of autism since genes associated with autism risk are not generally located on the XY sex chromosome. There are a number of hypotheses out there for the disparity of prevalence.
One hypothesis is that the disparity is more apparent than real: That girls are better at masking/adapting to their symptoms, and thus more frequently escape diagnosis. The first step is to determine the extent to which this is true. If true, the underlying mechanism would need to be understood...some have suggested this could be related to greater inter-hemispheric connectivity in girls.
I think that question is, why are girls better at masking/adapting symptoms? Regardless of whether autism is more prevalent in girls, what it is about being girl that makes you mask better.
There is significant pressure on girls to behave in a manner that an adult might (quieter, more sociable, smiling, tolerant of situations) and significant pressure not to behave in an outwardly or rowdy manner (stimming, being hyperactive, responding in upset at being overstimulated, responding to sensory displeasure by rejection, etc).
It would seem to me that masking works to a point (towards the "highly functioning" side of the spectrum), and once you get to the ways in which autism blocks ability to perform certain common behaviours and activities (e.g. non-verbal), the gender percentages should get closer again, because there's no masking to hide them or social expectations that they match. Is this the case?
It should be noted that this research sample, as opposed to many autism samples, includes autism with non-verbal, and severe intellectual disability phenotypes of autism, phenotypes not always captured in neuroimaging research of adults due to compliance issues (We collect neuroimaging data while participants sleep in the scanner).
My hypothesis is that there's is a simpler, more-cultural answer, which is that girls with autism simply aren't diagnosed at the same rate that boys with autism are.
One hypothesis is that the disparity is more apparent than real: That girls are better at masking/adapting to their symptoms, and thus more frequently escape diagnosis. The first step is to determine the extent to which this is true. If true, the underlying mechanism would need to be understood...some have suggested this could be related to greater inter-hemispheric connectivity in girls.