I'm not exactly feeling like downloading 13.2 GB to figure this out, but I'm a bit confused here: What does anonymized data dump mean? Does this mean the usernames are removed despite CC BY-SA license or what kind of anonymization is taking place here?
The data dump is basically identical to what's available in the Data Explorer, except in XML and offline.
Things like specific voting data and the users' personal information are scrubbed out, but we of course respect our own content license and usernames and association between posts and their authors are both available as expected.
You can download a much smaller data dump of one of the closed sites to get a feel for it. For example, Literature.
So far I've found the following columns that show on the public dump that differ from the presumed original internal SE values:
NULLfor most vote types, including upvotes or downvotes. Or else we'd know who voted on posts.
Votes.CreationDate: the time in hours and finer is truncated to 0: Why is vote time missing in the SE data dump and SEDE?
As stated in Database schema documentation for the public data dump and Data Explorer, the dump contains a
OwnerDisplayName field, so that's not the anonymization taking place. But things that are also not available online, e.g. who voted how, are of course not included.