Without a load revving the engine makes it spin tons faster than its supposed to spin, stresses all the parts. I am talking mainly about revving to say 5-6K rpms just to hear the engine note.
Think what Coca Cola might be trying to say is without a load applied, high revving can cause an oscillation in the pistons and crank, as the crankshaft eventually, at some threshold, will develop enough inertia to attempt to actually spin faster the pistons are being driven by combustion, and then dip below that threshold and inevitably lose that inertia, only gaining it back again after the next combustion cycle, where first the pistons are again being driven faster... this causes kind of a lash effect, a tug of war of forces within the engine that increases wear... would probably start to wear on crank bearings first, then as everything slowly loosened up, then rings, and cylinder walls... nothing ever actually moves faster than the other because the two are mechanically linked via connecting rod, so rpm = piston speed, at whatever conversion ratio applies given your particular crank circumference to piston travel length, but they will try to, given that the force being applied within the cylinder was meant to travel somewhere, and thus disperses throughout the engine via vibration even though it was designed to take it. I imagine this effect isn't noticeable unless you regularly exceed the redline for extended periods, and then cross back and forth between that line. They (used to anyway) do harmonics testing on engines to figure out at what rpms they started to hit their resonant frequencies and explode themselves. I'm pretty sure that goes into their redline determination as well.