Thanks @Licaon_Kter and @linsui for the additional info.
Apologizes for the premature logging of this issue!
I definitely should have known better - or at least should have checked my understanding. While I’ve been fully aware of the difference between free (freedom) and free (free beer), I obviously had some misunderstanding of the term FOSS (free and open-source software). I assumed the “open-source” part representing the free (freedom) character so concluded that the “free” part is in reference to free (free beer) 
I support the suggestions discussed in topic:paid-features-in-opensource-apps to inform f-droid users in a consistent way about a possible licence requirement. No need to call it anti-feature. It should be without judging the choice of a developer to go down this route opposed to donations to make the development sustainable. To make it easily recognizable for f-droid users would still help a lot. The detective work that sometimes needs to be done with GooglePlay apps to find out limitations/differences between the free part and the paid features/licence requirements is more than annoying and a waste of time. While it’s totally OK for me that a developer decides to go with a certain marketing concept, it’s not OK with me trying to hide it and lure people into installing the app by instilling wrong expectations. A bad start for a potential customer/supplier relationship…