My best guess is that they probably will keep the data for a few weeks/months longer for the inevitable users who forgot to archive it and/or missed the announcement.
I was thinking the same thing. "Deactivated" is different from "deleted."
I’m not a customer, but in today’s world, I would actually prefer that when the service shuts down, all accounts and published data are destroyed. Just wiped completely. Otherwise, what are the odds that customer PII gets sold off and the service owner licenses the previously hosted posts and comments to an AI company?