Am I correct in assuming from all your info posted that if you purchase the service Honda kit and the ESR adapter plate you will end up with an ignition curve that has less timing than the 2001 CR250 curve. And in order to get more timing you will need to slot the holes on the new stator plate?
I want to re-answer this question as I was incorrect because I had not yet removed the plates that center the stator at zero.
Typical Honda stators have a slotted top bolt hole and on the bottom a single hole centering plate that locates the stator. If you remove this plate then the the stator plate can rotate normally 4-5 degrees.
This Electrosport stator plate is different in it has 2 centering plates, I did not notice that they has sandwiched a top centering plate in between the bracket that holds the wires from the stator and pickup away from the flywheel.
When you remove both centering plates from the top and bottom then you can advance the stator plate just like a Honda stator plate which with no modifications you will get between 4-5 degrees advanced, if you want more than you need to slot the stator plate