This means that, averaged across many people, sex differences in brain structure do exist, but an individual brain is likely to be just that: individual, with a mix of features.

This is the better quote.

Gender has never been about "you are all male, all your features are 100% masculine" or "you are all female, all your features are 100% feminine". Not by my understanding anyways.

The point is that there are trends, and being a gender means you lean towards one side of those traits rather than the other. A man is far more likely to have shorter legs, smaller hips, or a larger X part of the brain. A woman may be more likely to have longer legs, larger hips, and a larger Y part of the brain.

And it also supports the idea that gender is non-binary, and that gender classifications in many situations are meaningless.

I want to know who came up with the grand idea that gender being "you are male or you are female" means "if you are male you must perfectly show all these traits" and "if you are female you must perfectly show all these other traits". People are well aware you can be a masculine woman or a feminine man, that doesn't make someone less a man or less a woman as a result. That's not how the terms have ever been used as I have seen their use.