This seems like a very academic and philosophical response but it's not really addressing the issue. If I say "do what you would have done without this information" how is your in-game path "informed" by your knowledge of the safe path? I gave you concrete examples, so tell me a concrete example of how you'd make a different choice under these circumstances because of being "informed" by your knowledge? If it doesn't change the result, it's not really a meaningful alteration of anything.
It doesn't though. I will give you the specific example, and you tell me the point where something has changed because of your knowledge:
Characters have been traveling overland quite a bit while adventuring. At first they sort of blundered forward but with experience they ended up with a set of strategies as follows: When traveling in unsafe and unknown overland territory the warlocks familiar flies up while invisible, staying in range of the warlock, and telepathically communicates the layout ahead and any potential threats to the warlock. Baring any threat or other known obstacles, the party tries to stay on low lying territory behind hills and trees and rocks to avoid detection by hidden foes, with a specific marching order which places a fighter-type in front which has a high perception, a fighter-type in rear, and the cleric in the middle, with the rogue and warlock between a cleric and a fighter-type. They will, using the reports from the familiar, maneuver around any difficult terrain or dangerous terrains like bogs and swamps and sandpits, and will take advantage of cover like forests and larger rocks.
Using this set of strategies and tactics, and comparing it to a map, you can tell pretty well what path the party will follow. Even without role playing it, you can just look at a map, apply this plan, and likely figure out a path the party will take. In this example, they'd follow a gully between hills, avoid a swamp to travel over to a forest, skirt the forest to get to some rocks, and only cross open terrain at points F and H on a map.
So now we know pretty well what the party would do if the players do not know the safe path. Once you introduce metagaming knowledge of a safe path - I am saying you still follow the path which they would have followed without that metagaming knowledge. WHICH MIGHT BE THE SAFEST PATH. We don't know if that path which is mapped out based on their usual plans is the safest or not.
You tell me how anything meaningful has changed in the game as a result of the metagaming knowledge using this concept? Don't be generic of "oh well they're still informed blah blah blah" be specific - what alteration happens IN GAME to the path they take? If the answer is "none" then the knowledge was meaningless in game.
Observation might alter the event on a quantum level, but it doesn't alter a D&D game