> Not sure if that's still true, but at the time it seems Fortran was a more restrictive language which permitted stronger optimization.

There is no aliasing in Fortran. In C (and using compiler extensions in C++) you manually use restrict to give the same information to the compiler, but it is a trickier process than in Fortran. Rust inherits this benefit from Fortran, but last I checked they had all related optimizations disabled (and most numerical computing friendly features in Rust tend to be on the back burner).