I once worked with a young cis woman who had a habit of telling people she wasn't trans even before they asked.
She did this because she'd been asked so many times she knew the question was coming. At nearly six feet tall, with broad shoulders, slim hips, a square jaw, and smallish breasts, she still plans on marrying a cis man and giving birth to children. Why not? After all, she is a straight cis woman. Her private parts are entirely female.
On a site like this, I would tell her, she doesn't need to tell anyone what her private parts look like if she'd rather keep them private. Nobody's going to be going there (or at least they'd better not be), so no expectations will be confounded in this area. But it would be a bad idea, I would say, for her not to mention what she looks like. Yes, she's a cis woman! But the natural assumption—and it is annoying that this is natural—the natural assumption is that a cis woman doesn't look like her.
I don't think anyone on this site needs to tell anybody what they've got in their pants unless they know it might do a bit of "reaching out," so to speak. But they should be straightforward about their body type.
And if they're not? That's not following site rules, and it's wrong.
And if their prospective buddy is so upset by this that they verbally attack them online? That's rude, and it's also wrong.
One of the things about human interaction: There's always plenty of "wrong" to go around. Wouldn't it be nice if one person messing up meant everybody else was suddenly, miraculously, perfectly right?