Changing a shared draft topic's category shouldn't be allowed

But you can only have Shared Drafts in the category you set in shared drafts category? You won’t be able to move a shared draft topic between categories, you would need to publish it first.

I think the bug here seems to be that Bulk Actions lets you do something that shouldn’t be intended.

Giving this a quick run-through on my test site, the Shared Draft I moved using the Bulk Action tools is now visible in the topic list for everyone, but inaccessible to a test user who doesn’t meet the shared drafts min trust level requirement.