I have also heard of this experiment. I would like to see it done with magnetic or other type of bearings that have very low drag. Every motor that I have worked with always showed signs of the current dropping and the speed increasing after a good warm up which allows the bearings to run freer. I have assumed that was the reason a motor accelerates faster the second time. Do you know of any demonstrations that would eliminate the bearings as part of the reason for the effect?
I like your idea for a test of two motors arranged in quadrature to test your theory.
The bearings resistance would offer a 'miniscule delta t' from the initial start-up IMHO. I like the idea of magnetic bearings though.
I'm still searching for more information on this effect. It appears to be very significant, way outside of bearings warming up. Various metal discs show different effects from reading. I'm unsure of the size of these discs if weight is kept constant, there's differing densities to look at. If a magnetic arrangement is more reactive than a matched size/weight other disc then this throws that one through the window.
The interest is finding why this occurs. The word anomoly is used and this itself shows a lack of understanding. It warrants further investigation to attain satisfactory resolution.
Has anyone seen a replication on YT?
I've started searching for something along these lines and only found scribed info useful.
A test unit may be constructed as soon as time allows. Proof of the pudding is in the eating.