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Thor is the same way. He does not like rope toys, and won't even eat a flossie unless it's been boiled soft. He loves to play, but almost exclusively with plush toys.
I think he either has weak jaws, or extremely high bite inhibition. He's little - only four lbs - but even though all his toys have squeakers, and he loves the noise, he can only make a few of them squeak.
We play tug of war, sort of. He doesn't really lock his jaws down and hold the way other dogs do. He sort of repeatedly bites at the toy and paws at it to keep me away. I have to try really hard NOT to take the toy away, he's so bad at guarding them. It's sort of pathetic, really.
Anyway, I just think some dogs are more into tug-of-war than others, just like some are monster fetchers and some are not. I would like to teach Thor Take It/Hold It, but I don't see pulling matches in our future. Hope this helps.