This was a design project,fool.
And the article presented it as such.. Just remember that when Lewis and Clarke began their trek to the Pacific Ocean, they did not take a powder-driven gun with them. Their rifles were air powered, using brass airtanks charged to 1200psi using hand pumps. Their firing mechanisms were so efficient that 40 shots of 47 caliber lead WITHOUT a measurable drop in air pressure.
Did I mention that these were French made guns produced before 1800?
Cut these folks some slack! Its a design exercise. The tubular steel of the frame may be used as air storage - who knows? If you have something POSITIVE to offer, do so. Otherwise, all YOU have to offer smells like so much HOOEY!