Roy doesn't/didn't really have a bad chin. If you're gonna base your defense on reflexes and fight with your hands down you're gonna get get cracked good and proper every now and then. Once you lose a step you've had it.

Just because a fighter has never been stopped, it doesn't necessarily mean they have a stronger chin than one that has numerous KO losses. A defensive minded fighter gets hit less than an offensive minded one. Does Floyd have a better chin than Gatti? I don't think so.