From what I gathered FTA it sounds like the author is putting forth the notion that Facebook is relying on old, mostly debunked theories around a "backfire effect" - when fact-checking increases polarization and results in the opposite of the intent of the fact-check.

The author then goes on to discuss how more recent studies (including their own research) and even some of the original authors of that pervious research had changed course and believe that fact-checking can indeed help course correct those misled by misinformation.

Therein lies the rub, according to the author Facebook's policies around the original research hasn't been updated to match more recent findings. This can be troubling given the stakes at hand.