What many do not accept among the claims of the Rust fans is that rewriting a mature and very big codebase from another language into Rust is likely to reduce the number of bugs of that codebase.
For some buggier codebases, a rewrite in Rust or any other safer language may indeed help, but I agree with the opinion expressed by many other people that in most cases a rewrite from scratch is much more likely to have bugs, regardless in what programming language it is written.
If someone has the time to do it, a rewrite is useful in most cases, but it should be expected that it will take a lot of time after the completion of the project until it will have as few bugs as mature projects.
Whether or not it was wise for Canonical to attempt to then take that codebase and uplift it into Ubuntu is a different story altogether, but one that has no bearing on the motivations of the people behind the original port itself.
You can see an alternative approach with the authors of sudo-rs. Rather than porting all of userspace to Rust for fun, they identified a single component of a particularly security-critical nature (sudo), and then further justified their rewrite by removing legacy features, thereby producing an overall simpler tool with less surface area to attack in the first place. It was not "we're going to rewrite sudo in Rust so it has fewer bugs", it was "we're going to rewrite sudo with the goal of having fewer bugs, and as one subcomponent of that, we're going to use Rust". And of course sudo-rs has had fresh bugs of its own, as any rewrite will. But the mere existence of bugs does not invalidate their hypothesis, which is that a conscientious rewrite of a tool can result in fewer bugs overall.
Similarly, sudo-rs dropping "legacy" features leaves a bad taste in my mind, there are multiple privilege escalation tools that exist (doas being the first that comes to mind), and doing something better and not claiming "sudo" (and rather providing a compat mode ala podman for docker) would to me seem a better long term path than causing more breakage (and as shown by uutils, breakage on "core" utils can very easily lead to security issue).
I personally find uutils lack of care to be concerning because I've been writing (as a very low priority side project) a network utility in rust, and while it not aiming to be a drop in rewrite for anything, I would much rather not attract the same drama.
No, they openly refuse to accept any GPL code.