I think it depends on how you define the terms. If you define a suspect chin as a fighter getting KO'd easily, you'd be right. I've always defined it as reacting in a way that leaves the vulnerable.Don't know how people can watch the Carwin fight and say his chin is suspect. Any fighter prior that took the shots Carwin was dishing out to Brock was done very early in the first round.
His striking defense was always the issue not the chin
I'd also say stopping the Carwin fight in the first wouldn't have been a terrible call. It could easily have gone either way.
His striking defense is indeed horrible, but his reaction to getting hit is every bit as bad.