They are userdatas, not tables. Try =type(Instance.new("Part")) in the command bar – you will see userdata in the output. It’s just invoking the __index metamethod of the instance.
_index can apply to pretty much anything. You can even set it to a function as long as it returns something. You shouldn’t see any substantial difference in performance if you did use that pathway. Having said that it’s a very weird way of accessing the properties of an instance.
Really appreciate this, that helped, im using it for Different Purposes than ususal that why it looks weired but if you saw the code it will make a lot of sense.