Nah, a container isn’t running nearly as much as an entire OS. Not by a long shot. The Kernel isn’t there at all and the entire device stack is gone. Most don’t even have an init system running like systemd. They’re closer to a chroot in a single terminal than running an entire OS.

The OS flavor in a container is mostly about what flavor of supporting tools are available inside the container. Almost everything else is a thin wrapper making calls in to your host OS or container services.