Re: "Not an uncommon story", you mean.
Unless you saw it yourself, and can give me the make & model of the drive in question. But you heard the story from someone else, who heard it from ... It's "a friend of a friend", all the way down, with no details. I was one of the guys who used to go out and trouble-shoot these stories (for DEC in my case). It always turned out that somebody got pissed off, ripped the drive out, and threw it at the wall/door/whatever.
Quite. Looking at those packs you'll see that they won't come apart and fling their platters around without a serious amount of energy being required. Way more than a linear drive actuator can deliver. Orders of magnitude more. One thing, the actual mass of the head carriage is pretty low. For obvious reasons. There's a hefty magnet as part of the positioner, but that one's stationary.
Yes, you'll ruin the pack, and quite likely the positioner as it rams into the end stop. But separating the platters from the spindle? Not bloody likely. And that would have to happen before the drive would start flinging the platters, frisbee-like, across the room.
One of the early DEC RK-series drives had a positioner that used a photocell and a striped glass plate as feedback. Unfortunately, the glue used to affix the glass to the positioner wasn't quite up to the task, and under heavy load (such as the drive exerciser) the glass had a tendency to become loose. Ergo, no position feedback, resulting in the positioner trying to join the heads with the spindle with great gusto.