[JonChesterfield]

That wouldn't be my guess at what "no compiler magic" implies.

Compiler magic means the implementation doing things that the application can't. It reflects limitations or constraints on the target language. If the language is expressive enough you can do everything through library code.

This would mean you're able to do simd vectorisation by hand, but you're also able to run a compile time transform that vectorises your code without needing to bind that transform into the implementation of the compiler.

Thus the non-programmer scientist can use libraries written by someone more on the boundary that do autovec etc, without needing to wait for the core mojo implementation to do it.