I think this stepped design is going to work well in exo-atmospheric conditions. Our endo-atmospheric electronics have the benefit of utilizing 2 separate heat transfer methods to release heat into the environment (radiation and convection) whereas exo-atmospheric only has one (radiation). So it makes sense that the stepped coin has a larger diameter at the other end of the chip being cooled in order to improve the heat dissipation if relying solely on the stepped coin for cooling, or efficiently using the stepped coin to act like a thermal vacuum to transfer heat to the next piece of the radiative cooling method (IE the larger side of the stepped coin can move more heat energy if each side is the same temperature (but lower than the heat source temperature, this creates a thermal gradient between the sides of the coin that then makes thermal transfer more effective through the coin using the thermal conductivity formula: watts per meter-kelvin where kelvin is the delta temperature between the sides of the coin).
https://upload.wikimedia.org/wikipedia/commons/9/9a/Simple_definition_of_thermal_conductivity-en.svg
Radiative heat dissipation requires a lot of surface area to transition thermal energy into infrared radiation that can be released into a vacuum efficiently in order to achieve a similar dissipation rate to endo-atmospheric equivalents.