I’d give the professional riders far more credit than that Nev. Its all about the timing of the pedal stroke and when you start to stand out of the saddle. The pause happens when people start to stand up when the pedals are at TDC or 6 and 12 o’clock. The standing pedal stroke should be commenced more at the 2 o’clock position so that your weight is already bearing down when you are commencing to stand. This allows for a seamless transition in speed when moving from sitting to standing position.