Well the point that I hope would be learned by now is that one should not assume "Aha! there's fundamental mass (matter)!" when all that is indicated is energy and process in a system.
I suppose that jumping the gun in that way would be called "Materialistc Fundamentalism" ....or is that "Fundamentalist Materialism?"
Isn't that what you'd call it?
BTW, the ancient Hebrews had a very interesting word for this kind of thing, which is translated into our word, "glory," It tends to be noticed as light, for example, but the root word is "weight." Maybe those folks knew something about QM... or something?
(OK, now you try composing a sentence with "stuff stuff is is.")