There is no need to have a packet on CRAN, 1 at all, and not to send anonymous packets to CRAN . Such a view would be a big problem for CRAN in terms of maintainability. CRAN is simply not the right platform for this.
Github has similar problems, but in principle, you can simply create a separate Github account without providing identifying information.
However, this simply poses a more serious problem: how is your code not really identified? More generally, the whole idea of a double-blind peer review is exacerbated by research identifiability issues. I do not think this is a good solution (especially using a code review, but even in general), where the research is anonymous. Thus, I do not think that it is worth spending energy trying to make anonymous representations of the code, to the detriment of the quality of software (service).
In cases where a double blind anonymous peer review is required, the best option at present is to transfer the code to a service that allows an anonymous archive, such as Figshare, or send the archive as additional material to the journal. The reviewer should not expect simple
install.packages(path_to_file, repos = NULL, type="source")
... otherwise they may not be qualified to view the code in any way.
1 Actually, this is not even advisable (on the contrary, I find that cluttering CRAN is quite counterproductive, although CRAN is “comprehensive” in its own name, ideally all its contents should be in the form of correctly used packages, in other words: quality, not quantity).