The change's effects are dependent on what each SKU reports as its Metal architecture, both as identifying string (the equivalent to running 'metal-arch' in the Mac CLI) and as generation 'gen' number. Most likely you're misinterpreting the change as not affecting the iPhone 16 Pro, where in fact it does.

The MLX folks have various rationales for not supporting the ANE (at least as of yet), but one of them is that any real support requires implementing explicit splits in the graph of computations, where ANE-suitable portions are to be dispatched to the ANE and everything else goes back to the GPUs. That's not necessarily trivial.