Since Adult Dragon is not something that low-level scum like Claude dares to mess with, that is why they deal with a dragon who is still young.
Yes, they deal with young dragons, technically a baby dragon if we look at the ageing prosses of dragons who live a very-very long life. And most ironic thing is that dragons have very high affection for their children more than humans as it is not easy for dragons to reproduce so for them every child is very precious, and if someone dares to come near them they immediately burn those guys to death. So people rather fight an adult dragon than mess with their children.