WE use the same material, heat treat, grinding, etc. specs as the military M16 specs. In fact, a suprising number of parts come from the same suppliers as the "other guys", so I doubt that anyone can base any such claim of "third tier" on facts.
The "other guys" must not even stake too much in these claims, since we often will exchange some internal parts during shortages, etc.. In fact, I bet if you polled many of the kit gun builders out there, you'd find the majority have our lower parts in them.