YOU DID NOT BUILD IDENTICAL TEAMS.

THE TEAMS MAY BE SIMILAR (BY COMPARISON), BUT NOT IDENTICAL.

THE TEAMS DID NOT PLAY THE SAME TEAMS WITH SAME FORMATIONS.

THE TEAMS DID NOT HAVE THE SAME LEAGUE, CL AND CUP DRAW.

Bottom line, the game engine may or may not suck, but your "experiment" most definitely did not test it.