To one degree or another, I think we all experience this phenomenon as I'm sure what he's referring to is the noise floor and at what point a system's noise floor becomes noticeable.
The author didn't mention if the subwoofer was connected to the AVR or not as even AVR's will introduce noise into a system in the form, if my thinking is correct, S/N ratio where the larger the number, the quieter the system. They also didn't mention if their test included isolation gear such as power stabilizers and ground fault isolators. If my understanding is correct, inductance can back feed noise into a circuit so someone's A/C or refrigerator next door can feed noise into a system.
Again, if my thinking is correct, normal S/N ratios are in the 96 to 105dB range and 105dB is considered neutral or black.
Maybe some who actually know what they're going on about can add to and correct any errors in my above.
A suggestion would be to give SVS a call and ask them about the comment you're asking about.