I understand that logic in theory, but surely it's contingent on the champ having a truly astronomical pick rate?
I mean, Lee Sin is the #1 picked jungler right now, but with "only" a pick rate of 28.71%. That's quite high, but that still means more games are played without Lee than WITH Lee, right? So, by that logic, if your teammate wants him, they have better than even odds of getting him, even at last pick.
If you're terrified of the pick on the other team then it's a way to hedge your bet, but it's also directly antagonistic to your teammate. I don't think that's worthwhile.