Female & Male builds as a game "rule"

In most game systems there is no differentiation between males and females, which of course is not how reality works but for most game purposes reality is fairly irrelevant. There is simply no game reason why the strength value of 13 should mean something different for males and females.
What almost all systems fail to describe is that this would result in the fact, that males and females look fairly identical. There might be some differences but the build would need to be the same in order to represent the identical stats. This is NOT, in any way what we see in movies or what our imagination provides us with. The differences are massive in that regard but they are ignored in the game.

However, if you would like to incorporate the differences between biological sexes and their specific traits into your game, it can be done fairly easy:
During character creation, you differentiate between a male and female body type and apply some modifiers as you and the player see fit.
An example could be that a male-build generally has a penalty of x for colour related perception or a bonus for speed-related rolls.
Alternatively, you could modify various stats by +/- 1-2, like a female build reduces its strength attribute by that value.
As that affects the various other values as well, it is my go-to solution.

With the ideas from the article Sexual dimorphism it is absolutely possible to ignore nature in that regard but still have a "believable and realistic" exit for the problem. You just have a character with specific biological sex but the biological "build" of the opposite sex.