We are running a small experiment where 0.3% of viewers will see an auto-generated thumbnail, instead of your custom thumbnail. We are not removing the ability to create your custom thumbnail, but we hope to gain insights on auto-generated thumbnails for the future.
Yeah, but it'll also hurt others. Let's say you're doing a play through, it makes sense for the thumbnail to have a generic thumbnail, just with the episode number changed. When you're looking through about archive of videos, the generic thumbnail helps a lot