OK it's not a prong collar prosecution but cruelty is cruelty. Well, that's the problem isn't it, it is not classed as cruel, but a training product.
I'm dead set against all of these pain related training techniques, trained 50+ dogs in my lifetime now and never needed to use pain or aggression even on the slow to learn and more stubborn dogs.
However all of my training has been with pups/young dogs. None need this kind of training ever IMO
GSDlover425 please train without it, I don't blame you, these things are quite the norm in some parts of the world, but a pup never needs a tool like this, far better to use whistle or clicker training, try to find a trainer who uses these techniques instead.

Training an aggressive or highly reactive dog, or living with such a dog..... I can't really comment on as such, tbh a dog like that, reared with these behaviours I would rather pts, wouldn't have the patience, G*d bless those who do, (months and years trying to re-train) a prong collar may make it think first, but does it really change a dogs character? Ticking time bomb IMO.
As for the coat, it will be a wait and see game until the adult coat comes in........tbf you would become curious and be impatient for answers if you had lots of people saying different things, even on here we can't agree

and we've been around a bit.