May I ask why? From my understanding Rust just have revamped their regex[0] using the same (similar) scheme as in RE2, which is now the Go's implementation, am I misinformed?
I'd also like to point out that Apple has a record of not practicing cautiously to security exposure, like _the inclusion of CNNIC root certificate despite the public exposure of security breach_.
[0]: https://github.com/rust-lang-nursery/regex/commit/e5a5198eee...