There are topics on this site I don't care to read - some mod specific topics for example. I've marked them 'not watching' and they don't show up in the regular unread topics. And they don't show up in updated topics, which is ideal.
But they show up in all unread because they're unread.
What I'm getting at is that all unread should respect unwatched the way regular unread does.
Tracked as #7402 (https://github.com/SimpleMachines/SMF2.1/issues/7402)
Fixed in 2.1.3.