I agree that it's odd, but it seems highly improbable that such a damning leak would come from his camp.
Not sure why City are doing this, as it seems highly counter intuitive, but maybe there's a method behind the madness.
If they have an offer from some club that includes some signing/agent fee if they drop the price down, than I could see the reason his camp would do it.
On the other side, I could only see it as some City's attempt to push him out if he refuses to go somewhere because of his wages.
But in any case, I think the story itself is a bullshit. From what I've seen before his loan to Sevilla, it doesn't hit me that he was unpopular in the team.