Lumen in the land of nanite is what he completely loaded into RAM, so that specific demo will run better on a PC.
Valley of the ancient demo specifically shows how Unreal Engine 5 is super efficient at streaming since the data isnt that large a PCIE4 SSD isnt actually needed to load in and out data.
Valley of the Ancient was used to show off how you could use Unreal Engine to make open world games that can stream in millions of polygons.
Test the demo yourself and see.
P.S We already have SSDs that catchup(read as trump) the PS5 SSD.
- PS5 SSD IO — 5,500MB/s reads, 5,500MB/s writes
- PNY XLR8 CS3140 —7,500MB/s reads, 6,850MB/s writes
- Adata XPG Gammix S70 —7,400MB/s reads, 6,400MB/s writes
- Mushkin Gamma — 7,175MB/s reads, 6,800MB/s writes
- Sabrent Rocket 4 Plus — 7,100MB/s reads, 6000MB/s writes
- Samsung 980 Pro — 7,000MB/s reads, 5,000MB/s writes
- WD SN850 Black — 7,000MB/s reads, 5,300MB/s writes
And before you come at me with the whole "compressed speed" thats not relevant right now.