My understanding is the way that Paradigm uses low frequency extension is in the context of what a listener might expect to hear in a typical room. Their frequency response is measured in an anecholic chamber, and the way that room acoustics work, it's highly unlikely that you'll get an in-room response within spec, especially as you get into the lower frequencies.

Just as an example, Paradigm claimed a low frequency extension down to 35 Hz for the Studio 40s. From my own in-room measurements, I will confirm that's true. However, it also does not take into account some of the room induced peaks and nulls that occur elsewhere in the 35-80 Hz range, and how that can vary in different locations within the same room. As with all specs, the low frequency extension is something you have to take with a grain of salt, and be aware of what influences real world performance.