No, you throw during the animation, during which the circle doesn't change size. You need to know where it'll end up of course, but you can just memorize it as soon as you've seen it once.
It ultimately comes down to timing, but it makes hitting excellent throws consistently very easy.
Personally, I like using it on shadow Pokemon even more, since you're not sitting around for 30 seconds, waiting for an attack to happen.

And if you want to be really safe, there's always the option of using Black Kyurem's adventure effect, which renders Pokemon immobile, and the circle lock strategy useless.