The FTC rule leveled the playing field between amp manufacturers! This was introduced in the 1970s because there were some pretty outrageous claims being made- get an early 1970s Radio Shack catalog and look at the power claims they were making. It was not uncommon for a 5 watt amp to be rated at 10 watts per channel- or higher, since there was no requirement for both channels to be driven.
The FTC rule is a very good thing.
The FTC rule is a very good thing.