"they are not lockfiles!" is a debatable separate topic, but for a wider disconnected ecosystem of sources, you can't really rely on versions being useful for reproducibility
It's also not about fully reproducible builds, it's about a tradeoff to get modern package manger (npm, cargo, ...) experience and also somewhat reproducible builds.
> modern package manger (npm, cargo, ...) experience
Lol, the word "modern" has truly lost all meaning. Your list of "modern package managers" seems to coincide with a list of legacy tooling I wrote four years ago! https://news.ycombinator.com/item?id=29459209
https://src.fedoraproject.org/rpms/conky/blob/rawhide/f/sour...
also of flathub
https://github.com/flathub/com.belmoussaoui.ashpd.demo/blob/...
"they are not lockfiles!" is a debatable separate topic, but for a wider disconnected ecosystem of sources, you can't really rely on versions being useful for reproducibility