Do you know how they do that? Is it something special about rust, or some process improvement they're doing?

For example, rustc has a very large test suite that is run on every single commit. There is also a language reference that describes the language in some detail. One of the things Ferrocene brings to the table is the paperwork and auditing that the test suite corresponds to the specification. With other vendors developing their own toolchain, they would have to do all three parts of that work (well, in the case of C or C++, two ish not three, since they have a specification, but there are always extensions and platform specific behavior to document) instead of just one. This isn’t the only thing they do, but it’s one example.

It’s not so much something special about Rust in an abstract sense, but in the practical sense that the Rust Project takes robust software engineering seriously, and being downstream of that is useful.