because unlike in the UFC video game, fighters "stats" don't stay the same throughout their career.
They're human beings. They get better, they get worse, ect.
The anthony johnson that fought lil'nog if placed into the cage with his past self that fought at ww (on a night he won or lost) would beat the shit out of him
Batman V Superman: Batman 3rd round TKO (Later fails post fight drug test for kryptonite)