This, and another factor can be whether a user’s connection is IPv6 enabled and working.
Situation where I saw something like this before was an instance where the admin didn’t include his server’s v6 address in DNS, so users were accessing Discourse on their v4 public IP, but Google Analytics was seeing them on their device’s v6 address so it was actually less capable of suppressing multiple views from the same user.
EDIT: ack! Just saw how old this post was. Not sure why it popped up in my new list O_o