Well it seems to me that a hypothesis about whodunnit is being turned into a fact on the basis of another hypothesis about the police using the press which is even shakier than the one it is supposed to support.
I agree that various media sources are hinting at GR being the culprit and hinting at his brother being his only alibi, and trying to pressure the brother to "come clean"... But I see no evidence that this comes from the police and I wonder if the journalists don't "know" it's GR because they read it on Websleuths
Here is the link, and whatever I think about Mirror journalism, the source of that article can only be the police.
http://www.mirror.co.uk/news/top-stories/2011/01/15/police-stop-shielding-killer-of-jo-yeates-115875-22850017/