But, if I decide that I had "heard this" somewhere, then how is that not meta-gaming. Sure, I can come up with some backstory bit that justifies it. You can do that with virtually anything.
So, am I meta-gaming or not?
At least the knowledge skill is leveraging the rules to justify why I might know this. Do I have the requisite knowledge skills? Then it makes sense that I know this. But, then again, the knowledge skills list is hardly encyclopedic.
My point about all this is "meta-gaming" is a very, very nebulous thing and is very hard to pin down.