I think you are confusing a logical network with a network namespace. A logical network is a construct of Docker or CNI or Netavark or whatever that acts kind of like a LAN. A network namespace is a collection of processes that the kernel treats as being one logical machine for networking purposes.

When you make a docker network that is attached three containers with hostnames a, b, and c, then those hostnames logically belong to the “network” (and your container engine may put considerable effort into making it possible for them to resolve each other and communicate), but there is one network namespace each for a, b, and c, for three total.

In Podman, but apparently not Docker, you can do --network container:foo to join another container’s netns. I assume that the reason that Podman and containerd support this low-level feature is that they both support some form of pod.