I’ve heard this expression many times and although there is some visual witness to this, as it seems, I’m not a big fan of expressing such action in that way.
Let me approach your question this way:
A whip has a handle, a length of neck and a tail end - the tail end is the business end of this device and produces the kind of report that gives this item its distinctive characteristics. And if you’ve ever seen a whip in action, the long neck actually bends a bit, in an arch, as the handle brings the entire length forward, and the “crack” that results from the tail of the whip being pulled back, and rather quickly I might add.
None of this action alludes to the arm during its pitching motion - none of it. I do not coach, nor do I even remotely suggest that the pitching arm should parallel the motion(s) of a whip. In fact, those pitchers that try and pull back any portion of the body so as to produce that “tail end whipping” action, invariably experience lower back and shoulder problems, sometimes preempted by abdominal and lower stomach stress and soreness.
What I do (did) coach, was a distinctive discipline for the pitching arm separate - but complimenting, the entire pitching cycle from beginning to end. And that discipline had basic elements, then adjusted for the specific physique of the pitcher that I was with.
Take a look at Roger C., pitching at the top right-hand corner of this web site and you’ll see classically stuff. Watch it over and over again, then, leave the page - start to make some assumptions and then write those assumptions down on paper, then come back and watch again and compare your notes to your second observation. ** A coaching style-method that works rather well I might add**
Notice how Roger C., controls his pitching arm, how he manages it in concert with his glove side, his leg lift, his forward motion, and his commitment to firmly planting his stride foot. I know this is only a front view, but if you study it enough you’ll start to see subtle details that repeat themselves over and over again.
To summarize, the pitching arm is controlled 100% of the time, from the time the hands break until the last part of the pitching cycle - at rest.
Now depending on your physique, your physical fitness, you ability to mobilize coordination and other related matters, so will your pitching arm draw from these assets.
I know this doesn’t exactly answer … do this … do that, but steering you in the right direction that fits your individual situation is my intent.