The fact they used Navi to do the targeting really demonstrates how the devs felt they needed to explain the new mechanic and not just use it 'because game.'
I know the "hold a button to lock-on to an enemy" was in Mega Man Legends, but in the first game you had to stand still for the lock to work. On MML2, you could lock and run around freely, but that game came after OoT
Love oot, but the only thing it brought 3d too was the Zelda series. Didn't realize about the lock-on mechanic, would've sworn it was in earlier stuff, but I guess not.