From a substantive perspective, you're thinking of a different area of the DMCA, for noticed related to copyrighted works. The RIAA notice at issue here was based on 1201, for tools used to circumvent copyright, and so it's not necessary to disclose the works being violated.
From a formatting perspective, format is generally irrelevant to notices like this because the law does not state a particular format must be used. Thus, any format which conveys the necessary information is generally acceptable.
Just because it's part of the DMCA doesn't mean it is allowed to be used in a take-down notice. Or at the very least such a notice wouldn't have to be construed as such. At least that's what I understood from this article: https://news.ycombinator.com/item?id=24888234
And while formatting is somewhat irrelevant from a legal standpoint it is still one of the tools Github uses to ensure that their take-down requests contain all the required information. Acting upon a request that doesn't conform to the format is risky.
From a formatting perspective, format is generally irrelevant to notices like this because the law does not state a particular format must be used. Thus, any format which conveys the necessary information is generally acceptable.