When dealing with anything in-game that characters do or can do, the rules are the social contract. If the rules say you can do it, you can do it; and if the rules aren't clear then you can (try to) do it until-unless someone or something tells you to stop.
The rules are
part of the social contract but not the whole thing. For example, the rules of D&D say if you have an ignited torch in your hand and there's a troll within range, then you can throw the torch at the troll, but the social contract of some groups might include a prohibition on “metagaming” that governs whether or not that’s a permissible action declaration.
The rules also say you can have your character walk anywhere you want as long as there isn’t a wall in their way and a sufficiently stable surface exists for them to walk on, and there are rules for slowed speed if the character is travelling through difficult terrain, let's say a field strewn with small boulders. But what if the boulders are somewhat larger? At what point do they become impassable and, thus, constitute a "wall"? The rules don't tell us this because different groups imagining basically the same situation are going to come to different conclusions on where “I continue walking across the field of boulders” is no longer going to be considered a permissible action declaration based on different genre considerations, conceptions of character capability, preferences, etc.
Another example is, when I cast
friends, the rules say I can choose a non hostile creature, to have advantage on Charisma checks directed at that creature. But what if, in casting that spell, I choose a creature that hasn’t yet been established in the fiction? Let’s say it
has been established the party’s in a tavern, and I choose a heretofore unmentioned barkeep, hoping to gain some much needed information. For some groups, I think that would be permissible. But on the other hand, if I choose William Shatner, the famous actor, stipulating he's present in the tavern, so I can try to persuade him to give me the keys to the Enterprise, I think for many groups that would be beyond the pale.
In the example of the backgrounds under discussion, the specific problem is that the wording of the rules allows those features to work in nonsensical situations. Thus, the wording of those rules needs to be changed by houserule such that those features work as intended: to wit, when it makes in-fiction sense that they would work.
A smart DM catches and fixes things like this before play begins. That said, the designers shouldn't be making a DM have to do this work in the first place.
What specific wording do you have in mind?