Yup, but other groups/teams can be non-staff and still be handling a category.
There may be limited number of staff users, and right now they have to be called upon to mark solutions to email in topic. This may give a large workload to staff when there are many email in topics.
That’s because if the owner of the topic is a staged user, he/she won’t be able to logon to mark the solution. And no other user with authorization to handle the category can do it for him/her.