I think it's just marketing.

It's amazing how little accountability is required to sell aftermarket parts. People believe everything a company says as gospel, whether it's a brighter, whiter bulb, a 10HP increase from a plastic tube, or better gas mileage from some snake oil. My favorite is the companies that quasi-scientifical high-tech-sounding explanations for their product's purpose, assuming that 90% of their potential customers will enter DUMMY MODE upon hearing it and immediately buy their product because the explanation goes over their head. I applaud companies that can deal with cold, hard numbers and dole out thorough explanations of how their product works and how they performed their design in layman's terms.

As for headlight bulbs, what I've seen is that pretty much every OE replacement aftermarket bulb that promises more light or "better" "white" light (the ones aimed at tuners, etc.) actually cuts down on real brightness out of the bulb. Not to mention that yellowish bulbs are better at not blinding other drivers.