Ahh, we are talking about the various makeshift cache techniques as one. I haven't seen him specifically talk about it, but I'm guessing the talk of extra copies of assets was how to easily explain it and basically say they won't need to reserve any extra space than they need. That's true, though games aren't going to get drastically smaller. They just won't be getting drastically bigger like this gen either, hence why the trade off is similar sized storage drives.
Developers have gotten increasingly lazy this gen with techniques and game sizes out of control. The buzz around not having to think about it anymore (at least on PS5) is more down to relief at not having to. Which is a good thing
Epic are the worst for un-optimised file sizes and ridiculous updates. But yeah, as above, they won't need to reserve as much of the SSD.