For as long as I've been aware of the feature it's been opt-in and _does_ have a privacy disclosure. FairEmail is better about its privacy disclosures than most apps are. Maybe they just didn't do it in the Google-approved way?

Preference that defaults to false: https://github.com/M66B/FairEmail/blob/master/app/src/main/j...

As to it being contact info, the file is literally called ContactInfo.java.