What should be the Vout for a CM-driven amplifier?
With an open loop amplifier, with colossal gain, and finite but unknown input offsets, you should regard the output voltage as completely undefined.
If you take any real amplifier from your spares box and wire it up like that, it's more likely for the output to be saturated on one or other rail as it is to be in the linear region between them. That's what should be expected from a design standpoint.
With a simulated opamp, it depends what the model for the amplifier does. If it is is given precisely 0 V for the input offsets, and a very large CMRR, then you may get a mid rail output.