RIAA alleges that it bypasses a form of DRM. Youtube tries to obfuscate the full URL of videos, so youtube-dl does a little dance to work out where to download it from. If this is a form of DRM, then the DMCA plausibly applies.

So, the argument is whether or not obfuscation is DRM? If that's true anyone can claim that some weird URL scheme is DRM. That's a dangerous slope to tread.

I think it is, too, but "is this sufficiently obfuscatory to fall under the DMCA or not" is really only something a court can decide- it's not a technical question. So "this is obviously not DRM" is an argument, but until a court says otherwise the RIAA seems to have a leg to stand on.

"is really only something a court can decide"

Sometimes I think the scope of what a court is allowed to decide is crazy. It allows new concepts to be manufactured for the convenience of muddying the legal waters. Why the hell legislate around "DRM" and then decide later what that means.

I mean, technically, can this be called obfuscation when Google provides to you the code to de obfuscate it?

That's how DRM usually works, one way or another.