Nope, you did postulate an unfounded fact. It isn't clear why the guy made sexual jokes. The author joined in a conversation she wasn't invited in on, and then one of the guys in that conversation made some jokes she didn't like. It's actually not clear whether the tone of the conversation between the two men changed when she joined it. For all we know that guy makes sexual jokes to his buddy all the time, there really are people who are like that. The author simply doesn't say anything about what the offending man was saying prior to her joining the conversation.

So yeah, you were extrapolating. But it does make sense to assume that the guy made sexual jokes because she joined in the conversation, and directed the jokes at her. In the story she tells about the developer making the joke about shaved pubic hair, she seems very reasonable.

It's a shame, the author probably should have been clearer that the jokes were made directed at her. Everyone has their own biases, and the problem with stories like this is that when women read them they think about the worst behaviour of men they've had to put up with, and assume that's what happened and when most men read them, they think about their own typical behaviour and assume it must be a misunderstanding.