Earlier quoted context omitted.
Apple allows you to provide an alternative API on OSX but not on iOS. Microsoft is exactly the same. They do not support custom APIs on Windows Mobile AFAIK.
> Apple allows you to provide an alternative API on OSX I'll need a source for this claim considering that no driver-level Vulkan implementations are available on macOS.
Developers can ask users for their admin password, sudo to root and largely do whatever they want including adding kernel extensions and drivers.