I can get cross platform rust up and building and running with 5 minutes. It’s probably half a day at least for c++ and a more significant maintenance burden.

Also, I think the “quick to prototype” only is beneficial if you know c++ and don’t know rust. I know both and I can say that Rust is much faster to prototype in precisely because

a) tests are trivial to add meaning it’s trivial to add test coverage vs in c++ you have to integrate gtest and bother to set that up which no one does B) many initial startup bugs are prevented. It’s not segfault after 6 hours but spend hours getting it to work correctly after it compiles vs it runs mostly correctly from the first build.

Even if Rust is slower to write (which is only true if you don’t know Rust and don’t have AI) it’s still overall faster to develop in. I can’t recall if MS or Google have written up their experience on that side or focused only on impact to vulnerabilities.