We are all different. The degree to which we allow those differences to limit our training, is the degree to which we will inhibit our learning. It is more important to me to work well with my partners so that we both learn, rather than become hung up on the stuff that really does not help our training all that much.
Short version: what he said.
"If men situations as real, they are real in their consequences." - from sociology, the Thomas theorem. This is the theorem that underlies the self-fulfilling prophecy. If you are convinced that your training partner, by virtue of his or her gender, will have certain predispositions, you will train in such a way that encourages them to act within those predispositions. Maybe you're completely wrong. Maybe you're at least partly right. But by reinforcing a predisposition, you're making it harder for your partner to behave any other way. You are, in part, creating a reality that supports your beliefs, and limiting your partner's ability to be anything else.
It's very hard to get people to understand just how limiting this is, unless they've been on the receiving end of it. When you labor under the restrictions of other people's belief in your (in)ability, it's like running a race with an invisible 40-pound sack of sand on your back. Some, a few, are perceptive, can see its effects and extrapolate its existence even if they don't feel it themselves. Most people will deny that that sack of sand exists. Then your "limitations" get explained as a natural inferiority. It's sort of soft-sell bigotry.