"Relatively flat" is, as one might expect, a relative term. I'm not worried that contractors might buy this and be disappointed, they know whether they can expect to have flat work areas or not, and won't consider this product if they don't.
To claim that this device handles uneven ground as well as sawhorses is just ludicrous. A pair of sawhorses can bridge swells, tree stumps, etc, and flex to conform to mild variations in their (small) individual footprints. Doing the "Infomercial Fumble", where you show some actor trying to use sawhorses improperly, as if he'd never seen them before, is unimpressive, to say the very least. The device will work very well as long as the work area is very flat, as in a driveway, garage, etc. There's nothing wrong with that. Why claim more?