Depending on when you look at it, it might be worked around or fully enforced again, it comes and go, but at least Youtube doesn't seem willing to give up that stance entirely.
To note, what u-block is doing to workaround this is far from the trival "just block the ad" behavior, and I expect it to break again (perhaps within weeks ?)
Then the waltz will go on as usual, until the ads are straight baked into the video-feed with the server refusing to serve the rest of the content on a per-client base.
I've never encountered this. What is it?