It’s one of those goofy stereotypes that make some people irrationally angry because they think that every thing needs to be fully inclusive of everyone and if it’s not then it’s bigoted. Saying bisexuals sit weird and cuff their jeans makes people who aren’t bi n do those things mad bcos they feel erased and people who are bi n don’t do those things mad bcos they feel erased but everyone just needs to google what a joke is imo 🙂↕️