Running on ported userspace components, with a shim, isn't the same as running on the OS in itself.

That really matters, sometimes.

But not the vast majority of the time.

(source: been coding iOS since pre-SDK iPhone OS 1.0)

Can you give some examples of where it matters? I'm genuinely curious.

Last I checked, VPN network extensions wouldn't run in the simulator.

Is the simulator faster than this? I would suspect so.