I don’t see how this is functionally different to passing an object that contains references to the relate to variables; which I’ll call a context object.

Practically, dynamic scoping is more confusing than context objects.

    void main() {
        int x = 2;
        fn();
    }

Does fn access or change x? You need to inspect the body of fn to know.

I would call dynamic scoping a poor form of coupling. Instead of bundling your coupling wires in a neat little set of in/out arguments and a return value (the format of which only needs the function’s declaration, not its definition), you are instead reaching out of and into the function’s body, like sprawling tendrils, as your function has free pickings of your variables.

It also strangely couples the names together. The outer function and the inner function may see the variable in completely different lights, yet dynamic scoping requires the outer use the name prescribed by the inner.

Optimization would be hard without WPO. You’d essentially need to keep a run-time “scope” object for every function. Though, the author’s proposed design for dynamic scoping in C++ means you don’t need it for every function; however that design has its own issues: how would you optimize such a design? It would a puzzling challenge.