Provide an example, please.No but in the context of the game world, which is something youre either purposefully ignoring just to make your point, if you tell the PC's what Hill Giants are and what they are capable of theyre going to get an idea of how dangerous they are. That has NOTHING to do with CR's.

Do they know whether the PCs are the equal of an adult red dragon? Now? In a month's time when they've gained four levels?The NPC's know NOTHING of CR's...

How do you know? Someone might come up with something elegant and comprehensive.There are no UNIVERSAL fixes.
"So there's this guy, see, who knows all about the campaign world's monsters and NPC villains and hidden dungeons, exactly how tough they are, and all about you guys, and what you've been up to for your entire careers and all of what gear you have and all your skills and abilities..."So having an NPC in the game that knows more than the PC's is metagamey? We were specifically talking about a mentor type right? Who said anything about the PC being omniscient? Youre kinda taking this to the extreme now arent you? If the NPC is there strictly for guidence or support then what's the problem or are the PC's supposed to just get all of thier information from where exactly if no one actually knows more than they do?
You see no problem with such an NPC, and don't understand the references to Elminster?
Fine by me.It's pretty obvious our styles are really different and there is no middle ground here so lets leave this conversation alone for now.