I’m not a lawyer, but a couple of lawyers told me two years ago that a valid DMCA takedown request should technically contain “Identification of the copyrighted work claimed to have been infringed,” and that DMCA 1201 is not the same thing as DMCA 512, which covers takedown requests.
Also, Suyu has claimed it does not include the same circumvention measures as Yuzu.
But those lawyers also told me that valid or invalid, it doesn’t necessarily matter all that much, since a platform like GitLab doesn’t have to host anything that it doesn’t want to host. It may not be worth the time and effort to push back on an invalid DMCA takedown request to protect something you might not even care to protect — particularly if the alternative might be Nintendo coming at you with an actual lawsuit.