I think there are some dog/handler teams that can't achieve their goals purely positive. Might a different owner/handler achieve that goal with the dog in a positive manner? I think probably. And, I think that some handlers can get positive methods to work with some of their dogs, and not with others, but that doesn't mean that positive methods would not work with the dog, just not with that handler.
But that is just an opinion. I think a good trainer measures the handler as much as the dog when suggesting how they handle the dog.
Jenna, RN CGC & Babs, CD RA CGC HIC
Heidi, RA CGC
SG3 Odessa, SchH1, Kkl1, AD
Ninja, RN CGC & Milla, RN CGC
Joy, Star Puppy, RN CGC
Dolly CGC & Bear CGC