How does this person know who, historically, is and isn't a woman?

Also, this person goes on a tirade about how the "original point" was about a very specific and conveniently unprovable "historic oppression." Meanwhile, the original comment actually reads:

Men have always and still to this day take credit for a woman's work

That comment is clearly not limited to some nebulous "women are property" medieval period. It's talking about right now.

How does this person know who, historically, is and isn't a woman?