The tire sidewall has more hysteresis than the air in the tire so it's always going to be a less efficient way to support the weight of the bike on a road with any roughness to it. On a vehicle with four wheels you want a short stiff sidewall to support cornering without tire deformation. Higher profile tires with flexible sidewalls always get better gas mileage.

Colder temperatures add an additional confounding aspect, and that is a change in air density which will increase aerodynamic drag so it likely won't prove anything regarding the effect of sidewall stiffness.