If you want everything to move as one piece, reducing the mass of moment arms is key. Unfortunately for that assumption, a moving car is filled with dynamically moving parts. Yes, he made an assumption that holds some merit in a situation where you want something to remain static. I honestly think he just made it based on looking at the car and thinking "well that's a solid chunk of rail, it MUST be keeping the car stronger/stiffer. that's another story - but it provides much more in terms of both safety and rigidity than the crash bars. I honestly keep a front bar for the utility of mounting a radiator screen and oil cooler more than anything else. It's a good idea to keep *a* front bar, but the rear bar is more or less useless. Subaru chassis' also provide GREAT protection for the fuel tank by mounting it fore of the rear diff./suspension assemblies. The rear bar might reduce frame damage a bit, but you'll never (or should never.) have the additive forces of two cars hitting head-on. The chassis has areas designed to absorb energy in an impact. The rear bar is, again, a blanket guideline in the USDM.
The engine, and how it moves during impact, is the single most important safety element in this situation. I've been in front-end collisions, both on and off a race track. The front subframe (U-brace) allows the engine to submarine and act as the dead weight in a front-end to absorb energy.
These happen to be blanket (legal) guidelines and Subaru's chassis doesn't *need* the added protection from a safety standpoint. The non-USDM tubular front bar and lack of rear bar is sufficient for performance, but USDM regulations require a larger front and rear bar for "crash protection". I guess the scrubs at Subaru should have added a rear bar in all models that didn't get imported into the US.
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