Sorry, I had over 10 pages of posts to catch up on and just skimmed most of it, but now I have time to respond:
That part wasn't meant to be snarky, but to illustrate that knowing the basics about a person doesn't mean you know everything. No, I don't have "proficiency" in survival (I don't hunt, for example), but one day I found tracks in the snow at my house and wondered what kind they are, and ended up learning a little bit about how to differentiate feline tracks from canine tracks. It's a random bit of knowledge that has nothing to do with anything else about me.
Which is why I said upthread that if the player can give me a reasonable explanation as to why they feel they should have such knowledge, I am perfectly happy with it. And then I would have you make a Wisdom check (since you don't have Survival I didn't include it.

).
And no matter how much I told you about myself (that's already WAY more than I usually reveal on the Internet...) there would still be countless surprises. So I find that letting players decide what they think their character knows results in a richer, more 3D character than otherwise. Sure, ask a player how their character knows something: not as some kind of test to pass to see if they are allowed to know it (and thus are allowed to take an action) but as an opportunity for adding some depth to their character. If they don't have something colorful to add, and just say, "I don't know," just move on.
And this is simply a place we disagree. PCs know what they know (or at least know "well") based on the aspects I outlined (backstory, proficiencies, even ability scores, etc.). Give me a good reason if a piece of knowledge isn't covered by one of those aspects, otherwise your PC doesn't know it...
What I found interesting is that you tried to parse the information I gave you in game terms: class, proficiencies, lineage rather than skin color. Even though I wasn't giving an in-game example. Not quite sure of the implications, but I guess I thought you were making some kind of realism argument...that one
could know what knowledge somebody else had by knowing their background...and maybe you're instead making some kind of game rule argument? (If so, I think it's different from the kind of arguments
@Lanefan makes, albeit with the same conclusion.)
Realism is a big part of it for me, but that is because without a strong base for it in my game, the fantasy falls short of being exceptional. That might not make sense to others, and is hard to convey via online discussion, but my players get it and are happy to play that way--they have actually said they enjoy it more.

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Yeah the Star Wars thing was meant to be a little bit snarky, a little bit funny.
Fine, a little bit both.

But it still wasn't really an accurate assessment.
I think the point
@Charlaquin was making (and I made up-thread) is that just because you can distinguish knowledge you have from knowledge your character has doesn't mean you are able to accurately make a decision for your character
as if he/she didn't have that knowledge. The human brain simply can't compartmentalize that way. The simple example I gave earlier is to imagine that you, the player, know the way to the treasure room. To avoid metagaming, you make your character go the other way. But if you didn't have that information, how do you know which way you would have chosen? You would have based the decision off of something else...a hunch, a clue from the DM, a guess, a habit of always choosing the lefthand passage, etc. The question, "What would I, the player, choose to do if I didn't know that information" is
impossible to answer accurately.
Actually, it is not impossible, you just have to understand there are more options. Here are a few that I typically do if I feel my player knowledge is too influential:
1. I let others take the lead most often in such situations.
2. I roll randomly when I have simple choices like the left/right treasure room location example.
3. I ask the DM if my PC would have certain knowledge (based on my own backstory, background, ability scores, proficiencies) and make a check if the DM agrees.
Now, maybe that's fine for the anti-metagaming rules you impose on yourself, but don't kid yourself that you are making a decision "as your character".
Most of the time, I am. In the case of monster knowledge. If I see no reason why my PC would know XYZ is a weakness of monster ABC, I will have my PC do what I imagine they would do otherwise. In other words, I have NO REASON for my player to exploit that weakness when they would not know about it.