Not to mention, if we're talking about IPv6 addresses, they often get allocated as /64 (or even /60 or /56) blocks. Such "anonymization" becomes useless at that point.
Google Analytics has nothing to do with this. As clearly linked in the mailing list, you can read the paper and source code for the client-side differential privacy tech used.
Which, according to Google’s FAQ, https://support.google.com/analytics/answer/2763052?hl=en, just blanks out the last byte of the IP.
Which is useless, because it still includes enough personalized data as to be completely and utterly reversible.