I have implemented the fix and got it approved in the span of about 3 weeks (and that was over the Christmas!). Doesn't seem that bad to me, given that it's a change that will affect pretty much any Rust user by default.
It didn't really require establishing a working group :) That is just an effort to improve Rust binary sizes in general.
In the end, changes in Rust can take a very long time (years) sometimes. It's maintained and developed by volunteers, and it has been growing exponentially these past few years, so not everything can move forward as fast as we would like.
I noticed a very tiny typo which doesn't affect behaviour I think. https://github.com/rust-lang/cargo/pull/13257/files#r1464506...