Agreed. I actually thought WK would've beaten him in the rematch through targeting AJ's lack of head movement. That's how WK managed to knock him down last time. Had he been more ruthless at that point, I think he would've won.
I think him not having the energy for the killer finish may be the reason for the retirement. Easy to say that he should have just finished AJ but what if he couldn't ? Has had a think about it since then and thought that was the best he had and AJ is only gonna get better. I think he's made the right decision.