Nothing is more ridiculous than the person who says all dogs are the same and that "it's just how you train them." Complete bullshit. Different breeds come with different codes within them. The amount (and to some degree type) of code can shift a great deal from dog to dog even within the same litter.
These pups are 7-week old Belgian Malinois and their hard-wired natural joy in predatory biting is being encouraged and directed at a very early age.
"The code explodes."
The puppy trainer here is not only encouraging them to grip (a core part of Schutzhund and Mondio Ring work), but also to ignore any explosive sound that will come from the "bad guy."
Restraining is a core part of training working Malinois. These dogs want to bite and grip -- it's self rewarding behavior -- which is why these dogs are NOT, NOT, NOT to ever be sold to, or acquired by, pet owners looking for a "watch dog."
You want a watch dog? Get a Dachshund, a Jack Russell, a Beagle, or even an Italian Greyhound. All you need is a dog that can BARK.
Malinois do not make good pets. These dogs are best reserved for people who have already demonstrated, through years of action, their own personal internal discipline and commitment to dogs by previously training another breed of dog to a very high level of performance. These dogs are NOT for the novice, but for serious, experienced dog trainers for whom dogs are the tent pole of their life.