It is a good test althougn it will need many samples to consider it a proof (either way)

I guess through friendlies will be the best to check this, sticking to one opponent , same counter formation same tactics both ways etc. So you exclude the oppo factor.

Just a small check i had. I power trained with same drills simultaneously 3 defenders.
I was expecting that the one with higher condition skills would be affected less by training
This did not happen so I stopped bothering .

Looking forward to your outcome good luck