"When the hardware is ready, the software will be comparatively easy to develop." I take it you've never written any software for a robot? The long tail of the real world takes years and years to handle. Probably the most advanced robotics company, at the cutting edge of the ML+Robotics, is Covariant and their entire business model rests on an understanding that the long tail can and should be handled by humans.
I agree that OpenAI is right to cut out the hardware, but all your reasoning about why is wrong.
The reason, which they state, is that data collection on physical devices is slow and modification to those devices is slow and maintenance on those devices is expensive. You want to simulate everything, not because it reproduces the real world in high fidelity, that doesn't matter, but because it gives you approximations with sufficient variety and complexity that you can continually challenge your AI, and you can do all that at 1M fps.