Neither a prophet nor scripture is a necessary component of religion. The classic religions of the Greeks, Romans, Germanic tribes, Africa, and the New World, had neither of these things, and the list is not exhaustive by any means.
Granted, but it's an anthropologist making the comparison, not a Mormon. I read "difference in kind" as religion vs. not-religion, where Mormon could just as easily be Ishmaeli or Shinto.
Then again, those religions where not absolutist as for example the Abrahamic religions are. I think especially the distinction between polytheism and monotheism explains a lot of that.
Religion is too broad a term, so there are subclassifications. You mentioned "absolutist" for one.
If one were to talk about religion in general, the definition would probably be close to encompassing nation states and corporations too: an intersubjective idea, that exists as long as people believe in it, and that evolves independently of any individual or group of believers.
