I find that the most common usage is for someone describing what they think is a small, very specific fact, but is in fact just a repetition of an old wives' ta

I find that the most common usage is for someone describing what they think is a small, very specific fact, but is in fact just a repetition of an old wives' tale with no veracity whatsoever. So maybe the original definition isn't intentionally used that often, but it does end up being relevant quite a lot!