We're getting fooled and thrown off by the looks. Yes, it looks funny (different) but it does get attention which is probably the desired result.
A large circumference equals smoother ride.
Narrow tire means less rolling resistance.
Long narrow contact patch equals the same traction is possible.
In the end, the gas milage would probably improve a little.
Acceleration is dead without a gear ratio change in the transmission.
So as is, he traded acceleration for getting noticed and a few more miles per tank of gas. Just sayin out loud.