It feels like perhaps you’ve conflated the issue in this thread, which is about using Rust in apt, which is much, much later in the distribution bringup than this bootstrapping, and using Rust in something like the Linux kernel, which is more relevant to those types of bootstrapping discussions you posted.

apt is so late in the process that these bootstrapping discussions aren’t quite so relevant. My point was that at the same layer of the OS, there are many, many components that don't meet the same criteria posted, including perl.

The procedure to produce GCC you cited was 13 steps. Many of the tools were made after distributions required GCC. And a similar procedure could produce a Rust compiler.