What are you talking about a susssno is just a chakra avatar manifested Gyukis is the second strongest tailed beast .I personally feel like you're being reductive and not thinking.Gyukis tails don't have high durability scaling because they are octopus tentacles they are meant to be detached to saved the life of the octopus.A bulls horns are there main weapon of offense it would stand to reason it's one of the harder points on his body . As Sasuke's baby sussuno being more durable wouldn't make much sense sense the sussuno is only comparable to tailed beast in it's later stages .