I think what SDC was trying to point out was that they used an arrow without a nock as the "target" when they split an arrow. In other words, you didn't have to hit it *quite* as squarely in the very center to get your arrow to travel down the shaft and split it. But we're talking about making the task about .5 millimeter easier.
I've split arrows, too, even a couple of times on purpose, but the ranges at which they're doing it are pretty impressive--and doing it on demand is the *real* trick.