Re: Yeah They're Wrong
If the programmer is really at a level where they don't know how wide an IEEE double-precision floating point value is, perhaps they might also be confused with what the "f" is in "f64".
Nor am I convinced by the ownership argument which wasn't expanded upon, unless by default all variables are const unless specified otherwise, which could be something to enforce better programming practice... or a pain in the backside.
You mention following good design patterns in C++ saves a lot of debugging time later. From what I can gather it seems Rust's main advantage is it doesn't have older design patterns which people fall back on so removing foot-gun opportunities. There are a tonne of paid-for static code analysis tools which can do similar for C and C++, but like code reviews, business is loathe to spend the money on them.