If you read the response letter the EFF prepared you'll see their argument was that the "rolling cipher" yt-dl worked around was not an actual protection measur

If you read the response letter the EFF prepared you'll see their argument was that the "rolling cipher" yt-dl worked around was not an actual protection measure. They contrast it with widevine, which is. There's a good legal argument yt-dl was legal in the us, and there isn't for the repo you linked to. I think standing up for things that have a plausible argument that they're legal in the US but not things that aren't is a reasonable line for a corporation to draw.