As soon as the reversal starts, that is when the first element is completed and the next element begins. It is now that the judge decides whether the reversal point was accurate or not and scores accordingly.
Even if there is supposed to be a hesitation, the judge still has to decide whether the reversal point was accurate.
Most will hesitate because it is easier to do the reversal that way. Flying correctly starts with the judges. If the judges downgrade for a hesitation, then the flyers will start performing the reversal with no hesitation. As they should.
Just because a top level pilot performs a maneuver a certain way, it doesn't make it correct if it isn't how the maneuver description says it should be.
Full scale flying technique, really has nothing to do with how we fly pattern.
Judging a120 degree point isn't really any different from judging a15 or 30 degree downgrade.