I find if you freeze waves against assassins, you risk them comboing you for attempting to freeze. A good example is a Katarina hiding outside of vision. If you pull the wave to freeze, she has full reign to just jump on you. If you keep the wave push into them, it takes less time for you to react to the roam. This is especially true for champions like Talon, where you are significantly slower to responding to the roam (with his E enabling him to roam faster). So, if you decide to freeze the wave, you have to first push the wave and then roam, and by that time it'll already be too late. Does that make sense? Thanks for the comment!!