My argument probably is that establishing some base rules that all simulations follow and some interchange standards is the key part of the metaverse concept. If you don't have that, then you have x separate unconnected "universes", but you can talk about a metaverse only if you have linked them in some ways.
You go in a lot of detail about the "Staff of Westfall" topic which rises some very hard problems, but not all of them need to be solved for a "minimum viable metaverse" (and perhaps not all of them should be solved - likely the optimal spot is somewhere in the middle between those two opposing wishes) - however, there's nothing metaverse-like until we do at least the basics of such connections e.g. ability to link and/or transfers of users, names/identities/aliases and at least some aspects of avatars; and in the case if two simulations are sufficiently similar and want to interoperate, then developing common standards to enable that avatar/item transfer.
Like, it's okay for a particular simulation to have a rule "custom hats are okay, but magic staffs have to stay outside" - but then it needs a protocol that allows them to separate different "accessories" of incoming avatars. And it's okay for a particular simulation (e.g. a virtual conference setup) to have a rule "magic staffs are only decorative items here", but then it needs a technical process to obtain the visual aspects of that staff so that it can properly display it with the new avatar - the simulation might be very different (VR, different styles of 3d vs 2d environment vs perhaps textual representation), so such standards are nontrivial but necessary to have a connected metaverse. (If we want to have it. Myself, I'm not so sure, but some people definitely do)
And if a simulation wants to allow the items inside but have a transformation to fit their specific mechanics - or even transform meaningful items to fit their theme (e.g. a space opera rpg representing the "Staff of Westfall" as a lightsaber) then there should be a standard for that "receiving simulation" to obtain the relevant attributes of that staff so that it can make that transformation, then they should not have to implement a different technical integration for every other simulation, that should be part of the metaverse standards.