The Rust stdlib doesn’t come with a CSPRNG so the point is moot. On the other hand, if you’re rolling your own crypto you deserve what you get if you don’t know the difference between CSPRNG and PRNG & you can name them differently even (e.g. rand(), insecure_rand()).
This was in response to the size of rand & dependencies, trying to be the safe default for every use. I don't have a strong opinion on whether it belongs in the stdlib.
