It's not the CPU or the i/o.
It's that the random read and writes are the same. Or random reads for games specifically. So I don't agree with the OP, at least that's what I think.
All these SDDs perform more or less the same in games because random reads are way lower than sequential reads. PS5 and XSX touting 5gb/s are sequential reads, but it'll be interesting to see if people can test them for random reads? with high queue count and low thread rate that is more like a game.
Sequential read and writes
Random Read and Writes
from Tech Deals.
Anyways that's just my opinion. The difference is between SSDs and regular hard drives and how many people on PC will still be using the old hard drives and whether devs will cater for them.
This is why it's always disappointing when Optane is left out of these comparisons.
But it's also why people should not be discounting hardware offloading/decompression.
Let's say that it gets you a 2x improvement across the board.
In the case of the XSX, it makes a 2.4GB/s drive perform like a 4.8GB/s one.
The typical PC gamer response is "well I can buy a 7 GB/s drive now".
But those drives might be 2.4 GB/s sequential and 0.5 GB/s random for the XSX; 7.0 GB/s sequential and 0.5 GB/s random for the PC.
The hardware offloading/decompression turns that into 4.8 GB/s sequential and 1.0 GB/s random - potentially up to twice as fast as the drive in the PC in real-world usage.
This is why things like DirectStorage and RTX I/O are still important, even as drives themselves get faster.
I'm surprised they didn't use Control as a benchmark. That's a game with longer load times than one would expect.
That's because the game is badly designed.
Loading times are tied to frame rate, and the game forces V-Sync on in the menus/loading screens. It's also slower in DX11 compared to DX12.
I ran some tests a while ago, and it took about 10 seconds to get into the game in either DX11/DX12 mode by default on my 100Hz monitor (100 FPS).
Forcing V-Sync off allows the game to reach its internal limit of 240 FPS while loading, which halved it to ~5s.
When limiting the game to only 24 FPS as a test, DX12 mode took 20 seconds to load, and DX11 mode took 30 seconds.
Control is not the only game where this is the case, but it's not that common these days.
Dishonored 2 is another game which was affected by this to a lesser extent. Its load times are also affected by frame rate, but its default behavior is to disable V-Sync and any frame rate limiter while it's loading.
If you're forcing V-Sync externally via the GPU driver, or setting a frame rate limit externally via tools like RTSS, you're going to see that load times are slower than they should be, because the game cannot disable those.
This is frustrating because the best-practices for G-Sync are to force V-Sync on and limit the frame rate to something at least 3 FPS below the maximum refresh rate. In my case, I typically limit games to 90 FPS @ 100Hz since that provides ample headroom; but also allows things like 30 FPS videos to play smoothly.