The point of having a rule set that can be pushed to like the system described here is that it can be fed information from a centralized task force. Indeed, these systems are used across industries with patterns and rules to detect malware, hacking, and a host of other activity (using formats such as STIX or TAXI).
It's unlikely that Facebook itself would be trying to determine whether a post to some content is propaganda - it's more likely that their automated system will apply the rules it receives from information defense agencies.
As per your other note, the selective censorship of information is absolutely a form a propaganda of its own. Facebook (and the US government) don't have the best history here and have 100% certifiably censored information to prevent effective organization of (for example) May Day protests. I'm not going to go speak about that at length here - hoping to get some technical clarity from those involved.