You are criticizing nynx for something they didn't say. As mentioned in another subthread, Linux is working on Rust support but only for drivers at this time.
Nynx did not say rewrite linux in Rust. They said apply Rust for making a secure ASN.1 parser, which is exactly where Rust should be applied to maintain safety properties.
Rust is being applied to multiple commercial operating systems at the driver level to harden them against known issues. Windows is already running Rust code in its USB subsystem.
While it's technically true that Rust encourages safe practices, it's not a blanket fix-all for everything.