But of course it would take much longer than a month to extradite him anyhow, so the most likely explanation is that they haven't had time to decide if they have enough evidence to extradite him, let alone to do it.
(IANAL)
Let him keep his passport and there's every chance he'll just turn up of his own volition to speak at a conference, give an interview, or pitch a new venture.
I don't think a jury would look kindly on playing so dirty with someone who posed no clear threat and didn't even seem to be on the run. And I don't think it would be right to either, until there's enough evidence to bring charges, he's presumed to be an innocent man in the eyes of the law. (We are of course free to come to our own judgement as individuals.)
All he's doing is giving interviews. Even if he's lying through his teeth (as I believe he is) - it's still his 1A right to do so.