I'm not a developer of native Mac apps. If I were, I would definitely have a baseline machine for testing.
The Stable Diffusion XL model is ~13GB
That's not a baseline consumer application. See my other reply (re: grandma and little Billy). If you're developing a native Mac app for grandma and little Billy, Apple probably doesn't want you shipping a 13GB model with it. This is an example of the point I'm trying to make: find a way to compress the model so the end user doesn't have to deal with that kind of bloat (or host it in the cloud).