Not really, it's pretty key to the propagation of the species to find certain genitals and sexual traits attractive. Those that don't notice them or care about them are outliers in humanity.
Yes, and that's not a bad thing. Anyone outside of the average in a trait is an outlier. Being 7 feet tall makes one an outlier, being a genius makes one an outlier, etc...
Is their preference really any more arbitrary than the preferences sapiosexuals or demisexuals have? It sounds like they probably have other traits that may make someone more or less attractive, they just have a minimum requirement for a certain body form for them to begin having attraction. That isn’t so different when compared to a sapiosexual who requires a high intellect before they can begin being more or less attracted based on other traits.
TL;DR: All preferences are weird, no need to call anyone out on their specific ones :)
Not OP, and not disagreeing with you, but I think it's also fair to point out that "having boobs and a vagina" isn't always preference for straight people either.
Some people are just hardwired to not feel sexual attraction unless the other person fits their needs, I think? Just like how most gay men don't feel sexual attraction to the aforementioned qualities.