Ofc UE5 has optimized their engine for PS5's SSD, they want devs to use their engine, even on PS5 exclusives, so Epic can make even more money, kinda obvious.
What he meant by 3rd parties can't leverage PS5's SSD is the fact that it would break the game if you use the PS5's SSD in a way other platforms can't keep up. So they can't make something that would break the game if SSD speed was lower than a set target. (dependencies in other components/modules etc.)
So define what's "breaking the game"? Because, again, game development on major titles is quite scalable these days, provided the money is there to enable it. I'm not saying it would remove every difficulty for developers, but at the very least it would greatly ease the process for them to harness the hardware features in a way that's manageable if the engine itself can help them scale performance across platforms which I'd expect a next-gen game engine from Epic to be able to do.
Here's the thing; if stuff like resolution, graphic textures, character model polygon density, lighting effects, physics systems, particle systems, AI etc. are greatly scalable, why would I/O feature sets suddenly not be? Those other things are dealing with processor complex doing much more work than the SSD I/O yet are pretty scalable depending on how a game is programmed beforehand (plus tools and engines have enabled better scalability on those things).
I just can't see how it will be so difficult for 3rd-parties to leverage the I/O features of PS5 in multi-platform releases, especially the major ones, in ways that are also very much scalable to other platforms without require massive rewrites of code or game design. And this would be an overall net benefit for all game developers on the engine. Epic seemingly wants to make I/O API tools as scalable and flexible in their engine design as any other type of technological feature, it shouldn't be impossible for them to implement. Otherwise if only 1st-parties would be able to leverage the I/O advantages of Sony's solution outside of faster loading times, I really don't think Sony would've bothered investing so much into such a solution in the first place.
The same can be said for MS; I'm sure they are working with engine devs like Epic to ensure 3rd-parties can use such engines to tap into their hardware's advantages as best as possible, and as easily as possible. Some aspects of MS's design may not necessarily translate as well to providing simple/easy access of exposure to devs through an engine like Unreal due to facets of its architecture being a bit more complex, but the vast majority of the hardware features I'm sure they want to ensure can be used relatively easily in the engine. Especially considering MS studios tend to gravitate to Unreal anyway.
