Statically provable memory safety is probably possible in some sorts of code, like business process logic where performance isn't critical, and you can use std

Statically provable memory safety is probably possible in some sorts of code, like business process logic where performance isn't critical, and you can use std:: containers and copy everything. A browser is a much more demanding environment, involving code generation, multithreading, caching, and low-overhead interfaces to complex data structures. Memory safety is extremely hard in that case. So both could be true.