YouTube is currently experimenting with server-side ad injection. This means that the ad is being added directly into the video stream.
This breaks sponsorblock since now all timestamps are offset by the ad times.
For now, I set up the server to detect when someone is submitting from a browser with this happening and rejecting the submission to prevent the database from getting filled with incorrect submissions.
If they are injecting ads into the actual video stream; it won’t matter what client you use. You request the next video chunk for playback and get served a chunk filled with advertising video instead. The clients won’t be able to tell the difference unless they start analyzing the actual video frames. That’s an entirely server-side decision that clients can’t bypass.