I think some part of this is anti-bot. They don't have a good solution to this yet, I and someone else I know got a lifetime ban from Meta just from opening an account.

No actions / no posts. I guess they determined the way we opened the account was too bot like. Sucks because we're real people that were trying to buy Meta ads.

But maybe doing something like this allows them to ease those restrictions, and then by charging for posts they have an ability to determine bots from non-bots in a more robust way. I'm doubtful it will actually work - because bots are exactly the type of thing that can and will try to open dozens of accounts to get around the 2 posts per month limit.