It is sexist because it promotes the myth that all women are flexible. They are not, just not all men are inflexible (hello, Jason?).
I find it to be the opposite: that women are actually better than men when it comes to this spin because they are more flexible in general at peak athleticism and I have no problem highlighting that. Much how women I think are just better at balance beam than men are, but I don't ask that the entire event be eliminated because the apparatus is somehow sexist.
topic: There are a few men who tried beam for fun with minimal training, and their skills are so much better (better amplitude etc.) than the women's (examples). So no, women are not better than men at beam. The difference is that they are actually training it, while it doesn't even exist as an event in men's gymnastics. So naturally there's more variety and creativity when women do beam.