People claiming that the deficiencies in the paper are minor and wouldn't be blockers obviously have little experience submitting to academic journals. Other parts of Google doing deeply technical work probably don't have the same level of review as the Ethical AI group -- for obvious reasons.
There is usually a long back and forth -- there are even memes about the infuriating comments from "Reviewer 2" [1][2]. Omitting to mention argument-obsoleting developments in the field (from your own lab!) is more than enough to send you back to extensive redrafting.
To be clear on terminology -- a retraction is an academic black mark, and occurs to a paper after publication, usually for reasons of research misconduct. This is not an instance of that.
[1] https://twitter.com/redpenblackpen/status/113344056990719590... [2] http://jasonya.com/wp/wp-content/uploads/2016/01/PowerRespon...