Right, as with other complicated low level systems, Android sees an annoying but seemingly unending stream of bugs that would be either impossible or unlikely if you used Rust.

I expect replacing low-level C++ with Rust to result in improved platform reliability as well as reduced security bugs.

For every weird memory safety bug that is usefully exploitable there are a hundred more that just mysteriously break things and may be very difficult for a human to spot. My WebAuthn tests broke on my Pixel 2 on Saturday, I spent about an hour trying to debug the problem, wondering why it was happening now but not before and why it didn't affect other platforms - then I rebooted the phone and it went from reporting a "NotReadableError" about the secure local storage to just working.