Oh! Okay, glad I caught a bug, but that means I’m back to being confused 
Lemme use a specific example… on the site ‘The Grumps’, the oldest story in the RSS feed is ‘Arin and Dan from the FUTURE? AGAIN?’. It was uploaded 31st December 2024, and imported by me within the last few days. It’s 0:50s long:
When I right click > ‘Train & filter’, I can see that the story has the ‘short video’ tag because it doesn’t say ‘More from this site’, and that the tag is set to ‘dislike’ at the folder level:
However, despite this, the story still appears in my feed when disliked videos are set to hide:
This is the case for nearly all ‘The Grumps’ shorts unless I hide the entire title.
I’ve only started using Newsblur in the last few days so all my imports are post-’short video’ tag. And from your explanation, it sounds like the intelligence system works retroactively - there’s no reason for it not to filter a video if a disliked tag is present. So, from a user perspective, all I’m seeing is: ‘short video’ tag is present, but the video isn’t getting filtered out 
Let me know if there’s something I’m not understanding here with how the system works!
(Separate note: I can’t find any short videos that are missing this tag now that I understand how the UI should look. Please consider that part of my original post a non-issue)!