Retention policies are quite common in lots of companies. If I had to guess his posts were treated in the same way, but given it's FB of course there's an unnecessary lie weaved in, because well it's FB
It's entirely possible that they also intended to delete his internal (company-wide) posts, and ended up deleting them all in error. Posts from 2011 don't really serve any purpose other than to be a goldmine for disgruntled employees who want to cherry pick something controversial. Public posts don't have the same problem because they are written with heavy PR oversight, and deletion is pointless because they will have been scraped and stored anyway.
That's exactly what we observe now.
When Google was 10x the size of Facebook and preparing to launch Google+ the battle cry of "Carthage must be destroyed" was empowering against something that seemed like an existential threat to the company. Take it out of that time and place and its aggressive and creepy.
How many companies would make historical all-company emails accessible and searchable by future staff? Doing so means that companies now need to treat absolutely every internal email as potentially public and run it through an PR filter. That's a huge cost for a company that wants to move fast.
>> How many companies would make historical all-company emails accessible and searchable by future staff?
I don't know. Most of them? It's not really that hard...