Software and hardware companies that make product performance-specific claims "always" have test results to back it up. The testing, however, is done on controlled computers set up with specific operational settings enabled/disabled to merely "simulate" user conditions. The fact that it may or may not perform exactly the same on your or my computers doesn't make it false advertising.
These test set-ups typically are done with NO third party software installed that may affect outcome... in fact, the test computers may even be optimized with specific hardware to help prove claims. Caches may be set to not store info; cookies may have been disabled. The point is, they don't just go out into people's homes with a stopwatch and time how it works with your system.
Everybody does it this way -- if you don't think so, look at the rating for fuel economy on a new car, and then buy it and drive it. Chances are, you aren't going to get equivalent performance most of the time.
As for FireWire relevance, that has long been Apple's way of preventing claims against software operational dysfunctions when OS X is "installed" on G3-upgraded Macs that predated built-in FireWire.