That's a folk stereotype, not a rigorous demonstration that "intelligence" (in the appropriate sense) must cause worse social interaction, as your comment would imply.
Edit: To clarify, even accepting that (some narrow definition of) intelligence (associated with math) is anti-correlated with social skills, that wouldn't imply that someone who is already "good at parties" should worsen their social skills by improving their intelligence.
Edit2: I agree that my earlier comment was poorly worded, and that, if you knew nothing else you should expect "conventionally smart" people to have less social skills. But that wouldn't seem to be relevant here, for the above reasons. And charismatic people are intelligent, in a sense.
Ah, well, I wasn't even trying to imply that anyways. I was looking at the pros: better attention, better executive control, better focus. Whether he's great at parties is totally beyond my comprehension.
If the change resulted in you being less able to do what you did before because of a higher mental load from the environment, that would be evidence against having improved intelligence.