I have owed a "100% rottie" myself and I don't see anything that would say your friends dog isn't 100% rottie. So he has longer legs, big deal people with longer legs are still people aren't they. I knew people who bred rotties, beautiful dogs, father 140 and mother 120 pounds from very good backgrounds. They ended up with a runt on one of their liter literally looking long and lanky....more like a dobbie than a rot but she was still 100% rottie. We should all know...especially a vet, that you can never go 100% on looks. I get told by people all the time that my checked boxer looks like a pitbull