The definition of 'woman' is irrelevant here, as the conference is not strictly limited to people who are women or non-binary:

>Earlier in the week, the organization addressed calls to ban men from the conference by saying that "male allyship is necessary" to work toward overall inclusivity and also that federal law prohibited discrimination based on gender.

So even if you made people get their vaginas out when they checked in, there is nothing to stop people who aren't women by any definition from being assholes and attending a conference that's clearly not intended to be a space primarily for them.