This is a feature, not a bug. Yes you need the instance as well as the community name. This is akin to complaining that you can’t type in a URL without including the TLD (*.com, *.org, *.wtevs).
I am open to an explanation how you can expect to find a community without both pieces of information. There may be a less confusing way to structure the links, but the community name and instance name are basically required for a federated system.