I know YouTube will throw a video to an extremely slow archival hard disk where getting 720p requires waiting a few minutes for YT to (presumably) move it to some regular storage tier with reasonable write speeds. But I've never heard of there being rot on the actual data YT stores, and I imagine it's on the same policy as Drive files where they're globally redundant, or at least in two different DCs.
It actually seems better from when I last looked at it, but you can you still hear skipping and audio jitter around spots like at 0:18. I've seen similar behavior on Twitter video uploads over the last few years.
I've seen video corruption myself on this video: https://youtu.be/XmWgskZFkh4. It's fixed now but there were glitches in the video and audio for a couple of years but somehow got fixed.
