How many times have you been driving down the road and had the person in front of you hit their brakes, come to almost a complete stop, and then move into the turning lane? Probably more often than you’d like.
Most turn lanes are set up so that one can slow down in their lane of travel (i.e., let off the gas) and then ease into the turning lane to begin their stop to make a turn. The turn lanes are set up this way so as not to impede other traffic. You do not have to wait until the last moment to move into a turn lane and it is generally desired that you move into a turn lane earlier rather than later.