I had missed some information on my network monitoring app (RethinkDNS[1]) and updated my last comment before seeing your reply! You're right about the connections to a Facebook server, though I'm only seeing the connections when the app is cold-started on Android. I haven't had the chance to test on iOS.
The Facebook Android[2] and iOS[3] SDKs are source-available.
From a privacy perspective, when someone compares Google Maps to HERE WeGo, the question is whether using Google or HERE (plus the Facebook SDK) would be more of a privacy violation. I don't have a good answer to this question.
But from a market share perspective, HERE WeGo is a minor player compared to Google and using it instead of Google Maps would help curb Google's market dominance in mapping.
Of course, if a free and open source OSM-based app is viable for your area, I would go for that instead.
[1] https://f-droid.org/it/packages/com.celzero.bravedns/
[2] https://github.com/facebook/facebook-android-sdk
[3] https://github.com/facebook/facebook-ios-sdk