Actually, there is some truth to this effect.
When a tire is manufactured, additives are included that prevent UV/Ozone damage, one of these additives is a UV protectent wax. When a tire is flexing, it causes an effect called "blooming." This "blooming" causes UV protectent waxes to flex within the tire and migrate to the outer side of the tire, giving UV protection to the tire. If a tire is not flexed, the outer layer of UV protectent burns off, and eventually you will get cracking in the tire.
However, it sure appears to be nothing but an Ad to sell, what I would consider to be an ugly tire cover.
