Please bear in mind that Linux has used non-standard GCC extensions to C for decades as well. The tradeoffs here are their call to make.
Besides, at this stage, it makes perfect sense for Linux to use unstable Rust features. It was one thing to say Rust should be great for writing kernels, it's another to actually get feedback on how it needs to be better, and that's only possible if the potential improvements are motivated by those who need them and incubated without the constraints of backwards compatibility nor the risks of locking in permanent tech debt.
Rust's unstable feature concept was designed for exactly this kind of freeform evolution and it's working exactly as intended. As for the specific tradeoffs being made in Linux, its contributors are in a much better position to weigh those than we are.
Besides, at this stage, it makes perfect sense for Linux to use unstable Rust features. It was one thing to say Rust should be great for writing kernels, it's another to actually get feedback on how it needs to be better, and that's only possible if the potential improvements are motivated by those who need them and incubated without the constraints of backwards compatibility nor the risks of locking in permanent tech debt.
Rust's unstable feature concept was designed for exactly this kind of freeform evolution and it's working exactly as intended. As for the specific tradeoffs being made in Linux, its contributors are in a much better position to weigh those than we are.