There’s a balance. I have known plenty of women who felt it was not permissible to fart around people/in public ever. One would not even fart around her husband of 10+ years. Another would only fart when they were at home, in the bathroom. Another felt it was inappropriate to ever fart, even when she was pooping (as a result of this, she once was so constipated that she had to go to the hospital).
Whilst these are particularly extreme examples, they’re just instances of a general trend where women farting is stigmatised more than men farting. I interpret the image in the OP to be resisting that excessive pressure and unrealistic standard rather than advocating for disregarding basic courtesy and farting with impunity
The point of “you don’t have to hold your farts in to be a woman” isn’t to suggest that only women fart, but that farting is a thing that people do, and that given that women are a subset of people, women fart (and that farting doesn’t make someone less of a woman)