It's a Linux (which is the OS that Android is running in) thing, it has nothing to do with manufacturer implementation.
The problem is that apps have to keep their current status stored any time anything changes. This is fine for an app that doesn't do much, but for a game with constantly changing landscape, it's going to be writing constantly. eMMC (internal) storage is designed for that, SD cards aren't, so if a game happens to end up on the SD cars (from adoptable storage or from your moving it there) you could destroy the card in a short time. (SD cards are rated in number of write cycles).
Adoptable storage was for 8GB phonse, to extend their lives for a month or two until you could replace them. It's not intended as a replacement for a phone with more internal storage. (You can use it like that, but don't complain when you start replacing SD cards [and have to do a factory reset every time, because the app is "installed" so you can't install it again, but it's not there, so you can't uninstall it].)