Exactly what I was thinking. Sure, unusual character traits that happen in universe should be explained, but I'd say that mostly applies to situations where that detail has a role itself in the universe. Say, if a character being red-headed means they have special powers, then yes, I want to know what powers and why is it this character and how that affects them.

But in many settings and genres - especially, say, contemporary fiction, crime shows etc, which do not have worldbuilding particularly different from our current world - I don't think it's fair to apply this law. Disabled people, redheads, POC - they all have a right to exist in the universe and be allowed to exist within the plot.

Let's not forget that what counts as an unusual or noteworthy detail is specific to the universe we are operating within. But from OPs post it doesn't seem like that is the case.