Complain with the executive. You also said XSX would run the same UE5 demo at 4k60fps and I'm still waiting for your reasoning on how it would achieve it.
Also it isn't only open world games that will benefit from it (and a lot of the AAA games nowadays are more open world game inspired than anything).
GPU and CPU on xbox one series x is more powerful. As I stated before, Forza horizon 4 already prove you can stream 4k assets at a fast rate on xbox one x, so the ssd won't be a problem.
Sure you can stream fast with Xbox SX SSD , and Xbox One X can stream open world games without having SSD
But we are talking about games with graphic like UE 5, a next gen graphic with has 8k texture and billion of billion triangles.