What are the properties/advantages of concentric winding?
The concentric winding produces a stronger filed in the center and weaker field by steps in the outer zones
This approximates the shape of a sine wave and reduces harmonic currents in the rotor.
(harmonic currents don't produce torque, only heat)
this winding scheme also puts two windings in each slot of the stator, (but elsewhere you say that some of the windings have more copper than others so there will be somewasted space.)
With a single the strength goes
 1  2  3  3  3  2  1  

The double option 1 goes like
 1  2  3  3  3  2  1  
            -1 -2 -3 -3 -3 -2 -1  

Which makes
 1  2  3  3  2  0 -2 -3 -3 -2 -1 

The double option 2  (1 red + 1 green) goes
 1  2  3  3  3  2  1  
             1  2  3  3  3  2  1  

which makes
 1  2  3  3  4  4  4  3  3  2  1  

I'm just counting ups and downs of the current