Maxperson
Morkus from Orkus
That's still not what metagaming means, and it still isn't relevant what the player knows, just whether the character could do what the character did or if it was impossible (and if it was impossible, that's still not metagaming - it's cheating).
There is a definition of metagaming provided in the book - it's thinking of the game as a game, and the examples provided are nothing at all like scenario described here.
You are getting caught up in the typical pitfall of worrying about metagaming - getting distracted by your knowledge of what the player knows, and missing that the knowledge is irrelevant (or, at least in my opinion, should be irrelevant) because the declared action for the character would be totally fine if the player didn't know.
And that is forcing the thing you claim to be trying to avoid - the player's knowledge, rather than the character's, determining the character's course of action - to happen.
The definition provided in the book is incorrect. Metagaming has specific meaning over decades. That meaning doesn't vanish because someone at Wizards got it wrong.