The stay of execution of Google's OpenID support, possibly until 2017,
only applies to ikiwikis that had already been live and whose
openid_realms had been
seen by Google in at least one request by 19 May 2014, or whose admins had emailed Google to
request an extension by 15 June 2014 ... this according to Miguel Andres's answer on
Google will not work as an OpenID provider for any ikiwiki set up since that time.
So, probably that Google option shouldn't be in the OpenID selector; maybe there should be an option: default off, can be turned on for an established ikiwiki instance that is known to be grandfathered.