The primary person at NSA who investigated him has stated publicly that it's unlikely to be true, due to the actions taken on his behalf by various individuals

The primary person at NSA who investigated him has stated publicly that it's unlikely to be true, due to the actions taken on his behalf by various individuals who appeared to be making sincere efforts to get him to South America (rather than Russia). He was stuck in Russia due to his passport being revoked by the Obama admin. That official did state that it's possible that Russian or Chinese handlers could have faked those efforts, but he still believes there would be some telltale signs and that the most likely conclusion is that he was not in fact a foreign intelligence agent. Somehow I doubt this random internet guy has a more informed assessment.