Unfortunately that is based on the Aristotelian philosophy, which is incompatible with mechanism. The “stuff”, with mechanism, is explained in term of statistics on computations (which requires much less ontological commitment than any sort of primary stuff that nobody can see, as “seeing” require interaction).
Physicist measure numbers and infer relation between measurable numbers. The 3p physical, that is those sharable number relations, is the object study of physics. “Physical” admits also a first person sense, like with “ a physical sensation”, which brings the mind-body problem, where, as the platonism philosophers understood, makes highly dubious that the physical can be used to understand the metaphysical, needed to justify the existence of the (appearance of) stuff.
The use of stuff in metaphysics is only slightly less naive, and as much invalid, than the use of “god” as an explanation in philosophy.
The god of the greek theologian (not of the greek myth and legend) is only the god of monism: the idea that there are first principle explaining everything. That is at the root of modern physics, but with the mind-body problem, we can guess that physics cannot be the fundamental science. With mechanism, Darwinism’s spirit is extended to the original and logical development of the physical laws from arithmetic. Up to now, the observation of nature confirm mechanism, and disprove materialism.
This is hard to swallow for dogmatic materialist, as many still exist in our Aristotelian (weak materialist) era. People confuse the serious evidence for a physical reality with evidences that the physical reality is primary, but that is simple category error, facilitate by the fact that theology and thus philosophy (which is just theology without a notion of God) are separated from science.
The difference between science and bad theology/philosophy, is that in science, we never abandon a concept of an idea, but change the theories and definitions when we get contradiction. We don’t say “Earth do not exist” when we learn that “Earth is not flat”, or” not supported by infinities of turtles”, or "not at the center of the universe”: we just change our views.
Mechanism reduce both mind and matter to only one mystery: our understanding of natural number, but it explains why this mystery is absolutely unsolvable. That explanation of mind and matter is constructive, making the theology of the universal machine both a pure branch of mathematics (even of arithmetic) and a testable experimental subbranch of physics.
In that Mechanist frame, the 3p physical is given by the “theory of quanta” obtained from the theory of the observable (defined with the intensional variant of G and G*), and the difference between G and G* (and the corresponding intentional variant) makes precise the difference between the sharable and measurable quanta, and the non sharable, but still experienceable qualia, which gives the 1p physical qualia. Qualia obeys a quantum logic which extends the logic of quanta, corroborating the fact that with mechanism, all the physicalness is obtained as a first person plural reality.
Bruno