If defence is about attitude, then when you are looking at 14 year old, I guess you are assessing their character not their technique.
Their willingness to engage in physical contact, not shrink when a big forward runs at them. Racing to get back in position when they make a tackle, diving on loose balls. Standing up to aggression. Character is hard to teach, the building blocks have to be there and a good culture will help develop that.
Sure, the technical aspects of defending can be taught and is not important when assessing kids. I think Luke is referring to that when he talks about defence. Without that Character, you don't have the basis for an NRL player regardless of how skilled and speedy they are.
Our players seem to have been picked because of their character. Commentators rarely complement our defensive technique.
Are the Panthers technically better than any other team when it comes to defence? I think no, but technique doesn't make Kenny dive on a loose ball, or try and smash a prop twice his size. It doesn't make Marto try and put the opposition into the front seats, or make Leota square up to rampaging props like Fonua Blake. It's all about character. Character = defensive resolve. Find the youngsters with that and you are on the way to building a good team. Find them with character + "X" and you are championship material.