I could maybe understand the anonymity, but I don't see why the substance of the feedback that let to the whole paper getting retracted was kept secret at first

I could maybe understand the anonymity, but I don't see why the substance of the feedback that let to the whole paper getting retracted was kept secret at first. At least give the paper's authors an opportunity to update the paper. The reasons Jeff Dean cited in his email for the retraction sound like things that could've been fixable.