Remember, the FAST idea actually means "Full (Range Driver with) Sub Transducer altho most of us just use a bass driver to avoid bass frequencies (<120Hz) coming from the FR driver with the obvious benefits - this has drifted up to about 150Hz in many cases but still is an approximation of FAST
In contrast, the subwoofer frequencies are below 80Hz (sometimes <60Hz) as this is where the bass become 'unidirectional', assuming high filter slopes
Just to be a bit pedantic, most room acoustic standing wave problems arise primarily in the 50 - 80Hz area and secondary interactions up to about 2 octaves higher (mainly in smaller rooms) - 8ft ceilings can be a big forgotten source of problems
BTW, why should we call "fullrange" if it cannot fully cover the 20Hz-20kHz? May be because we use it full range or without HPF and LPF? What if we use the enclosure for HPF (or other means for LPF) for example?
Yes, these terminologies are not fully accepted. I have difficulty when I want to refer "fullrange" to a driver (It can also be fullranger; note I wrote it as one word without space).