Yes, this isn’t a bug. It’s by design in the current incarnation of the code.
If your email is associated with an account then the posting rights of that account also determine where you can mail in to. The email is resolved against your account, and because your account can’t post there the it can’t create a topic. It would be stranger if you could because per-topic categories aren’t a thing, which means a topic would be created that you can’t see or respond to.
The current solution is to use a group inbox rather than a category for this kind of situation. PMs can have more granular permissions and enable this scenario quite well, we use it extensively.