Macbook essentially involved Apple hardcoding 11th hour fixes selected by product code in their OS level drivers after utterly fucking up ACPI tables in ways that would make the discussed bug blush. Pretty much most of what BootCamp did on later models, and what various hackintosh "special drivers" did, was fix things like HDA tables located in completely wrong place.

Steam Deck is just... extensively tested and debugged in ways that I don't think Apple did unless they got an egg on the face in national media (remember "you're holding it wrong?")