I was under the impression that those obfuscation methods were exclusive to certain YouTube partners, including the RIAA members. If youtube-dl stopped supporting that method, it would still be a useful tool for the bulk of its use cases and the RIAA would no longer have any leg to stand on since it'd no longer be able to download their members' videos.

Since this affects only tests, they could easily change the relevant scripts to download a list of test videos at runtime. I bet the RIAA github-scrapers would not "see" it. Just serve statically a rot13-encoded list of URLs from pastebin or something, and Bob's your uncle.

I suppose a developer that wants to make sure that it works with certain DRM schemes can add cases of their own, locally, without pushing the change.

feel free to file an issue and tell them that, but clearly it does work in this case.