Seems to be a visibility-only change to a small cohort of users.

Tangentially, I've often wanted a third button, call it "disinterested".

This would just tell YouTube not to recommend more of the same for me, without adjusting the ratio of votes up or down.

There are many videos I don't actively dislike (I might not have any strong feelings) I just don't want YouTube to recommend more cats with laugh tracks after I click a some link in our #random Slack channel.