> we already have results which show that the distinction between stack and heap is artificial and phony.

That's not really true on modern architectures.

The "stack" is a way to time-alias memory and, on modern architectures, that also has performance implications. The stack gets pushed and popped repeatedly so that area of memory stays very hot in the caches.

Garbage collection, by definition, trashes locality. So, pushing onto the "stack" and unwinding it by "garbage collection" is pretty disastrous for performance on modern architectures.