The example is entirely unconvincing. Why would you store those calls in a map and not just a variable?

Even if the map is crucial for some reason, why not have the map take a simple value (like a unint64) and require the caller to convert their string into a slot before looking up the function pointer. That way the cost to exchange the string becomes obvious to the reader of the code.

I struggle to find a use case where this would optimize good code. I can think of plenty of bad code usecases, but are we really optimizing for bad code?