The unified memory enabled developers to practically start using the GPU for things other than rendering. This in turn places higher requirements on an emulator

The unified memory enabled developers to practically start using the GPU for things other than rendering. This in turn places higher requirements on an emulator. None of the emulators you see today existed before someone sat down and started writing them. Your point about PC emulators is irrelevant since if you control the guest OS, it's just much more practical to install a pass-through driver.