Nothing is relevant outside of the steam deck. Steam is actively developed software that requires updating the kernel and dependencies on the device. All the hardware manufacturers like Asus are not using a dev team to maintain hardware compatibility and they will never fully mainline their source code.
It means all of the other manufacturer's hardware will depreciate quickly as software evolves in the real world. Hardware specs are a fallacy and completely irrelevant when the software they run is not static. When the software can change, the only relevant device is the one directly supported by those that maintain the software.
I’m guessing he is referring to the fact we aren’t going to see tailored updates like the Steam Deck has gotten over the years. Updates that improve performance and the experience. It’s windows so beyond device drivers and their terrible ArmorCrate software there isn’t much room to grow better. It’s not a bad device though, it just misses the point.
After watching the Gamer Nexus video of what's practically a warranty scam by Asus, I'd never buy one and may never buy Asus again if that's the way they treat customers. I have a few of their ROG components in my system and from what I see they are not as great as they were 30 years ago.