Same here. But after the unread, I would expect the first suggested “new” topics to be in categories I’m watching. After all, if it’s “suggesting” topics I might be interested in reading, then I’m more likely to be interested in those than anything else. And after those have been exhausted, then move on to other categories. But that’s not what happens. The suggested “new” topics always start with support, which I’m not watching.
Category preferences are not used in suggested topics at this time. However if your category is set to watching, that changes topic notification state in every (new) topic in that category, which is used.