Mike's right, the velocity can cross 0 without pausing, even though this means there is an instant where the cue is not moving.
For those who argue for an intentional pause, think about it in terms of muscle movement. Before the backstroke, the cue is at rest, and so the tricep must exert backwards force on it to start it moving backwards. During the middle of the backstroke, the cue is moving backwards, and the bicep must exert forward force on it to make it stop going backwards and start going forwards.
Now in that instant where the backward motion of the cue is stopped, if the bicep continues pulling forward like it was before, then the cue will start moving forward with no "pause" in the acceleration. The stopping of the backswing and starting of the forward swing are one continuous event. This is the stroke Mike idealizes, and physiologically it makes the most sense to me too.
If you're on randyg's school of thought, then when the bicep is done stopping the cue, it takes a break before starting the cue's forward motion. This means from the beginning of the backstroke through the forward stroke, the tricep exerts force, then the bicep does, then they both pause, then the bicep goes again. This is more complicated than Mike's version, where the tricep pulls, and then the bicep exerts force smoothly and constantly all the way through the back of the stroke and the forward stroke.
Muscles always pull, never push. I think you made a slight error. The Triceps pull the cue back (with out the help of the Bicep) and the Biceps pull the cue forward.
Also, thanks to Colin Colenso's shotput research, I know that muscles contract with more force when already under load, meaning that during the forward stroke, you have more available power if you haven't paused your bicep's exertion than if you had interrupted it at the back of the stroke. Having more available power means less effort and strain to achieve the same results, which can only be good for your accuracy.
Any counter-arguments from the SPF folks? I learned a lot that I find very valuable from my lesson with Scott, but I think this part of the SPF school of thought is flawed for the reasons stated above. Please no replies using the phrase "they don't know what they don't know" or "it has worked for thousands of students". I'd like to investigate this topic on it own merits using real reasoning, rather than see it dismissed as ignorance, which has happened in previous threads.
-Andrew