Spinning without load is not what steel vs ceramic is about anymore than rolling a 20PSI tire vs a 100PSI tire would tell you on an empty bike.
Smoothness - that is just lack of grit and round bearings - and viscosity of the lube. All are something, but it is the compression/deformation under load which is why ceramic bearings even exist.

Steel compresses more under the same load. So it is like a lower pressure tire and has a larger contact area.
At high speed - like 1000X what you would see on a bike that flexi - matters. It may matter on a bike too, but while I'm not making claims that are scientific, if not tested under real load, it is hard to say anything.