Well, it's not really FAA "policy"
The FAA are the regulatory enforcers, if you like.
It's the manufacturers data that must be followed for continued airworthiness, as the propeller was originally type certificated/approved with a protective coating. Removing that coating is an alteration and no longer complies with the design spec's. Even if you didn't intentionally remove the coatings and it simply "wore off" over time, you would still have a propeller that was not airworthy due to CONDITION, and even if the FAA never saw it, your IA should bring it to your attention for correction during annual.
