I actually think this is exactly the point. He is talking about how these people are highly intelligent but not successful because society isolates them and doesn't give them the opportunity and motivation to learn those skills in the appropriate window.

This is kind of the opposite of students that are underperforming that don't get the attention to help them keep up. Instead these are students that can overperform, but don't get the challenges, validation, and motivation - the general positive feedback - that will help them grow and succeed. Instead they are meet with disapproval and neglect since teachers both dislike them asking hard questions (thus challenging their authority among already hard to control kids) and don't have time to give them the attention they need (since they are most focused on the largest median group).

Yes, but this is not the case here. In particular, the author tries to solve the lack of social skills between people sorted in categories (thus by IQ in this case). So it's not that important whether they are 'intelligent' or not (the definition of 'intelligence' is controversial) but their integration into society (very poor so far, as the author shows). That's the problem the article aims to share.

High IQ creates barriers that can prevent one from experiencing the social situations that enable the development of social skills. And when you are left behind in social skills, past a certain age, people show much less tolerance for your quirks, and basically think that if you are that way, you must be weird/ have a problem and will not tell you honestly what is the issue with you. Giving somebody with subpar social skills social cues serve no purpose, as they don't get any benefit out of it. So you get a catch 22, as you don't have sufficient social skills to know / get the help needed to develop your social skills.