but that's only true for HDDs and SSDs that aren't using the proprietary standard found in next gen consoles. I very much doubt those would fit into the slot, so you'd need to connect them via USB 3.1 (some sources say 3.2 but whatever).
With these official SSDs, you can - of course - play next gen games from an external drive.
Therefore I don't understand why you'd need to reinstall or move stuff constantly. everything non Series S|X can stay on external HDDs or external SSD (non-proprietary) if you prefer.
Next gen games will either go straight to the internal SSD or the proprietary external SSD.
My issue was why can't I put next gen game on an external HDD. However I didn't notice the proprietary expansion slot. This is where the next gen games can been stored externally. Means no more uninstalling or redownloading them. Just rip out one expansion, and put in a new one when run out of space. Plug that one back in if you want to play a game that is on it.