This sounds right. It's not like girls are being deemed "the gold standard." Instead, there's an existing set of behavioral expectations, as you put it, and girls (for whatever reasons) just happen to have an easier time conforming to these expectations.

If societal expectations are things like: kindness, respect, agreeableness, calmness, paying attention, not talking back, not fighting, and so on... and girls tend to conform to these while boys tend not to, that doesn't necessarily indicate a conspiracy against boys.