It is a "title" being applied in this instance due the the more limited extension. Many (perhpas myself, included) would prefer to think of any Subwoofer worthy the "title" to be capable of 20Hz at a minimum, with Infrasonic extension a heavy preference.
If you are planning on using the Speedwoofer in HT, it will not extend deep into the unheard portions of LFE content. Yes, cabin gain can possibly create some extension, but this is not predictable in any room.
End of the day, it is one of the many trade-offs that one must consider while shopping for Subs in the small and inexpensive categories. You just have to decide what is important to you, and what you can allow yourself to afford in pursuit of that.