I think the concern is that the core argument that "I think Linux should adopt rust for safety" is a bit dishonest, given that there are a large number of well-vetted alternatives. "I think Linux should adopt rust because I like rust for social reasons" would probably be more correct. That Google staff seem to think rust is good for the Linux kernel but not, say, Zircon, would be surprising if those same people actually believed that any legal rust program is safe and inherently trustworthy. "Embrace, extend, extinguish" wasn't that long ago.
I think that is a false perception created by the dev-blogging community. Based on GitHub activity (https://madnight.github.io/githut/#/pull_requests/2021/2) Rust usage is declining (absolute numbers show little growth). Based on developer surveys (https://www.jetbrains.com/lp/devecosystem-2020/) very few people use rust outside of hobby development.
I think the concern is that the core argument that "I think Linux should adopt rust for safety" is a bit dishonest, given that there are a large number of well-vetted alternatives. "I think Linux should adopt rust because I like rust for social reasons" would probably be more correct. That Google staff seem to think rust is good for the Linux kernel but not, say, Zircon, would be surprising if those same people actually believed that any legal rust program is safe and inherently trustworthy. "Embrace, extend, extinguish" wasn't that long ago.