The title already existed because it was prophesied. For example, prophets had long forseen the coming of the messiah. Jesus fit that description so he was "worthy" of the title. One could even say he "looks like the messiah."Maybe I shouldn't come back to this after it being buried a few days, but I've been away. Anyway, I've been playing Ocarina of Time 3D: Master Quest lately, and I just came to the point where Link enters the Sacred Realm for the first time after pulling out the Master Sword. Rauru tells Link, "Only one worthy of the title of 'Hero of Time' can pull it from the Pedestal of Time…." Of course Nintendo wasn't planning on making Skyward Sword at the time of making Ocarina of Time, but to me this sounds like the title Hero of Time already existed, and Link needed to be older to earn it. The Master Sword was locked in the Pedestal of Time ever since Skyward Sword, and the only one worthy of wielding it had to resemble its former master—SS:Link. Through this, OoT:Link would become worthy of being the Hero of Time.
A little bit later, Sheik tells Link, "You really do look like the Hero of Time." This wording is just awkward unless there is a previous Hero of Time like whom Link could look.
I agree that those two quotes are a bit awkward, but they do not outright contradict the notion expressed through several other quotes that the title is legendary because it describes a future (present, now) event - not because of an event that has already happened.