Every automaker that I know of does the same thing. After final assembly, the car gives into a dynamic vehicle testing (DVT) booth where the car is placed on a dyno and run up through the gears at speeds. Exhaust, brakes, ECU, various critical systems are computer checked while the technician does this brief, aggressive test. The tech also notes whether the car feels right (no odd bearing feeling or noise, brake pulsation, etc.)
I asked an engineer at a GM assembly plant DVT station the same question posed above.
He answered that the brief, aggressive testing was required to ensure all systems were functioning properly, to document certain systems met legal requirements (emission controls & brakes, maybe others), and to set misc seals.
He said the test is intentionally very brief to keep internal engine, brakes, and transmission temperatures from getting very high. After DVT the break in period's main purpose is to properly burnish in various components that slide against each other (most with lubricant film) including brake pads & rotors, engine & other powertrain journals, piston rings, etc.