It's generally the difference between using it as a descriptor, and a noun. Noun bad.

Compare "I really like watching the female football game" and "I really like watching the women's football game"
"Female" isn't trans-inclusive, but people aren't going to look at you weird either way you say it.

Now compare that to:
"I really like watching the females play football." and "I really like watching the women play football."
"Females" here makes you sound like you're getting sexual gratification from watching the players, or that you see them as nothing more than a vagina, "women" sounds like you might like the game.