That is very interesting. It is described as a ported reflex enclosure, but it is not.
Lets add the FR
Notice there is only one peak of impedance and a very small one at that, and not two as there would be with reflex tuning. The nadir between the twin peaks would tell you Fb. So there is no Fb.
If you look there is a slight rise in output centered on 80 Hz, and then the roll off below that is 12 db per octave, not 24 until 30 Hz and then it rolls off 24 db per octave.
So this is not any of the reflex alignments. So that port has an unusual function, and seems to be behaving much more like the old Variovents on some Dynaudio designs from years ago.