He hasn't thrown him under a bus, quite the opposite really. The bus would have seen Jacko on the street, with 0 chance for another team and 3,000 leaks about everything he has done to the club.
However, the Neanderthals have grunted and found their lack of form and credibility sit on the shoulders of one Jackson Hastings and there is not a lot Twenty can do to maintain the locker room but to let Jackson go and appease them.
I am sure Twenty would like to "fix" it, from his words, but he has to take responsibility and maintain the wider teams view that he is credible.