This has been well known for many years now amongst those in the digital advertising business. And it's not just Facebook, but Google, Pinterest, Bing, Amazon, etc. They use vague definitions and slightly polished data to embellish the effect on marketing. For example, by Pinterest's definition, they consider a "conversion" to be an impression for an ad that converts to a sale sometime within the next 30 days, regardless if a user interacted with the ad (click, double click, etc) or had been exposed by an ad for the same product on a different site. It's an absurd metric definition.
No digital marketing managers are fooled by this. I mean c'mon, given these companies' track records, you wouldn't blindly trust their performance reporting. Those who manage ad campaigns almost always correlate performance to metrics that are measurable on their end. The most common are ROAS (return on ad spend) and revenue. I think the only victims of this may be the individuals and super small-time marketers with small budgets who are inexperienced or lack measurable business outcomes.