To my knowledge, this is not true: the CRAN servers historically produced and maintained traditional de-anonymizable server logs that included information like IP addresses, but the maintainers were historically unwilling to share those logs with anyone outside the core team. I’ve been on direct e-mail threads with the CRAN maintainers where they’ve declined to share that kind of data, but acknowledged its existence.
Things may have changed since then, but I don’t think you’re representing the broad state of the art accurately. AFAICT Julia differs from Python and R primarily because Julia uses GitHub servers for hosting most artifacts, so GitHub has all the of the truly private information for Julia users, but Python and R have that data for their communities because they host most artifacts directly.