I don’t think “female” is offensive.
I thought it was offensive because some (supposedly female) users said it was offensive; but I didn’t understand why my female friends used the term (female).
I found another saying that it wasn’t offensive, and I immediate copied that belief.
LGBTQ+ politics is confusing …
Great answer. Context, tonality and people’s mood/feelings vary wildly and are fundamental aspects of how someone will take such a thing.
Your last point is key - when unsure (e.g. not talking to a close friend), choose the most polite words.