I am not a fan of Facebook, but this is one reason they did not want to get into being the arbiter of what is true (Along with a lot of other less noble reasons). There are indeed things that are demonstrably not true, or presented in a very misleading manner, but there's a whole class of things that are in between.

The scientific world in general is a community where research about things comes in, people digest it, and come to a consensus. This includes some contradictory things or things that turn out to be faulty conclusions. This does not make them "fact check verified false". It is a stream of information that is weighed and honed over time with further research or questioning.

Now I agree people are very bad (even "smart" people) at ditching their inherent tribal nature to weigh data that supports their bias more highly. The echo chambers of partisans on social media will assign an impossible burden of proof against evidence that challenges their thought on something and have no burden of proof on the converse. But that does not mean that we can then make it binary of "true" or "untrue" to stop this. "Fact-checks" feel good, but it is clear now they are being extended to not just the realm of demonstrably false information and more into the opinion and inconclusive realm.