How does a "Slavyanka" motor operate with a reduced amount of copper?

Igor Korkhov told and showed on the graphs how a motor with "Slavyanka" operates with 8-10% less copper than the required amount according to the calculations.

The graphs demonstrated that the effciency of this motor slightly decreased by 0.5%, but the mechanical performance remained within the standard permissible range.
It turns out that even with the lack of copper in the winding, a "Slavyanka" motor keeps the standards high.

What happens when the amount of copper is normal?
A motor with "Slavyanka" has considerably higher efficiency graphs, mechanical performance, torque.

The conclusion based on the observations is the following: saving due to using less copper can result in decrease of certain performance values, but even with less copper in the motor we get adequate quality of motor torque performance within the permissible error range, with lower efficiency.