When you create a cult, you become the cult leader, and the first member of that cult.

You can't be the first member of a new cult, if you are already a member of another. If you want to create a cult, you will need to leave your current one.

No, it's not a bug, it is a feature. You just cannot be a member of two cults. It has always been that way, and will continue to be that way for the foreseeable future.

However, if you would like to suggest that users be able to join multiple cults, rock on.