Words mean what they do because there's a general consensus, rather than an absolute rule that is fixed for all time. The corollary is that people can use the same word to mean different things on occasion. For example, I can't take the claim that "not everyone who menstruates is female" seriously (beyond possibly certain rare genetic anomalies), because I have always understood female to be a description of sex and biology, and I suspect that everybody else on AB does too. But it's clear that Lilo is using it to mean something different, ie "female" is about gender rather than biology. Or, at least, I *hope* that's what they mean. For my part I can't agree with that definition, but it remains good practice to ensure you've properly understood what someone is saying before telling them they're speaking tripe.
On the other hand, I can't see the need to get so protective about pronouns. It's been flexible in English historically anyway: "If the salt hath lost his savour, wherewith shall it be salted?", and "aye, she's a fine ship" make it pretty clear that we are happy either to ascribe masculine/feminine qualities to inanimate objects, or that "he/his" etc was sometimes a catch-all before we introduced "its". In that case, there's simply no sense in getting so het up when a transperson calls themselves "he" when they were born female, or vice versa, because pronouns have never been so dogmatic.