Greg K-H's email acknowledges that mixed-language projects are difficult to deal with. But he makes a good mitigating point: they are all Linux kernel maintainers and developers, and they all already work on very hard things. They can handle this.
It reminds of the "broken window theory" [1] in the sense that when two windows are broken, breaking a third one seems not to matter (I of course don't suggest that Rust programmers are criminals; I have no proof yet ;-).
It is a trap one can easily fall into, e.g. "this method is already huge, adding a couple of lines to it doesn't make a difference".
You are right, but this is being hedged against the advantages of adding Rust. I daresay no one would agree to more work for no perceived benefit. If you want to contest this tradeoff, that's a different tack.
