I have two dogs with higher defensive drives than prey drive. They are both higher in threshold, and fairly clear headed. They aren't reactive and do decipher situations(even when immature mentally). I don't think this is the norm with most dogs that are more on the defensive side. I see a sharpness, maybe thinner nerve on some dogs that are more defensive, they react before they think. Others overthink, and won't engage because they are over analyzing a situation.
When it comes to my own dogs, we did put pressure on Karlo when he was young, it didn't do much detrimentally to him, it powered him up and he handled it well. After knowing more, I waited with Gambit to do any work on the defensive side....we tried to instead tap the prey, but his threshold was really high. So we waited him out a few months. Now he powers up and is balanced in the prey/defense.
Some dogs that are too high in prey are worked too much, too soon trying to tap the defense. Better to let that type mature a bit before putting pressure on.
edit my post after seeing the forum it is located in.
Pups/dogs with defensive drives naturally should be managed and shaped to learn they are to look at their handler in all situations for direction. They should not take matters into their own paws when young. IT is all about the handler being the leader/so the dog is not feeling the need to be 'on' all the time. That said, my above post about thinking dogs plays into it all. I want the dog to want to think, but not overthink and not react just because they deem 'a threat' when in reality it is not a threat whatsoever.
Balance is key so work the dog to that goal, no matter what venue you will or will not train in.
You won't really be able to see defense drive in a stable pup unless your do protection/bite-work. A stable, confident, clear-headed pup of good genetic nerve will not have to tap into their defensive drives unless they feel threatened and under attack. Defense drive is when they are defending themselves from attack - if you are thinking about them defending you when you are under attack, that is protectiveness, and is not the same thing.
Gryffon is a littermate to one of Jane's dogs' and is similar in temperament and working drive levels. He is a DREAM to live with! People friendly, easy-going, excellent "off" switch, good with cats, eager to please, bidable. Does not have that edge of suspicion that Jane's Karlo has, but solide nerve and and strong fight and defense drive, when brought out in training.