While I do assume that magic is the physics of the game universe, I don't presume to try to write the physics text book of the imagined universe. I couldn't even write a physics text book of this one (despite lots of college level physics, I'm just an amateur).
Besides, it would be boring.
Instead of working out every detail of the magic behind undead, I tend to define undead narratively as, "All the spooky stuff from folk lore about the restless dead.", and then make up the "physics" as needed to justify it.
But honestly, even something like a "Zombie", is not something that I've fully worked out all the magical physics behind to have some idea how exactly they work. I do some hand waving about being "powered by anti-life" and being "unsouled automatons" and usually that's enough to get players to stop asking questions, but exactly how something can be "powered by anti-life" and exactly how that works isn't something I try to reconcile in great detail. It's "bad" and "not good" and "dangerous" and that's good enough to run with.
I do applaud his attempt to root everything in a cosmology and have an origin story that explains, as it were, "How did the camel get it's hump?", or whatever it is that might need to be explained. But his origin story isn't very generic, conflicts in various minor details with mine (for example, animals and plants preexist the gods in my campaign world), and probably conflicts most D&D settings. As such, it's particular to his table and isn't really portable.
However, I suspect at the level of the stories he's trying to create, there is a lot of compatibility. For all the backstory he gives, none of it seems to alter how we'd expect undead to behave or how you might interact with them. He gives a very strong reason why all undead are evil (that neatly eliminates all need to worry about how you treat someone's dead mom), but we probably already expect that and in most games I'd guess "this is someone's dead mom" doesn't come up nearly as much as "roll for initiative".
