We'll return to "Listing Basics 101:" If the UL mark is not on the product itself, it's not UL listed.
Is it required? There's never any code requirement that something be UL listed. There might be, in some cases, a requirement that product claims be verified by an independent organization. This, however, is not one of them.
The product is, essentially, an appliance. It's not part of the permanent wiring- so the scope of the NEC is very limited.
Now ... COULD the product ever become listed? If so, how?
UL would, I expect, evaluate the product as a temporary power strip. Considering the claims made in the advertising, they would expect it to meet NEMA-6 requirements. Corrosion and aging tests would be made. Dielectric and current leakage tests would be made. GFCI tests would be made. It would be evaluated for 'tamper resistance' and overload protection. With the 'no spark' claim, I'm not sure what they would do ... no am I sure about the overheating protection claim.
(BTW, NEMA-6 'submersible' requirements are quite modest as to depth and length of immersion.)
I am concerned as to the 'special substance' they claim to use. You can be sure UL would focus on this in their aging and environmental testing.
A little note regarding the burnt receptacle slots they show in the ad .... the 15-A breaker on power strips notwithstanding, power strips are NOT expected to indefinitely supply 15 amps through a receptacle. Such scorch marks are most often caused by long-term use at maximum load; there's simply no way to run that much current through the feeble internal wiring and the plug contacts without something getting hot. A similar thing occurs inside the cord plug, where the wires barely touch the plug prongs.
Sanyo is a reputable firm, and Japan has a long tradition of very creative engineers. I'll give them an "A+" for trying to go beyond code minimums. Yet ... I'm not about to try their 'safe to lick' test!
