120 Hz might present a small issue if running 2 or more subs spaced well away from the speakers, but should not be an issue with one sub, as is the case with the OP. From the thread to which you posted the link:
"The author concludes that, based on the crossover frequency threshold values, there is little directional information contained in the sound signal below 200Hz, and none at all, below 100Hz. " Borenius 1985.
"At VDT by a simple show of hands, nearly all of approx. 40 attendees reported at 100Hz perceiving no “swirling motion” in monaural, but a definite “impression of motion” in stereo." Miller 2005. NOTE: Since the OP is using a single sub, the sub is outputting in mono (the mono signal is a combination of the stereo signals).
“I have found before that putting subwoofers that augment frequencies between 30 and 150°Hz at the sides of the listening position can solve spatial problems in many rooms!” Griesinger 2018
“Below 40Hz it's not as much of an issue, but between 40 and 90Hz, yes, there is "stereo content" possible in a good venue with a good recording."
https://www.audiosciencereview.com/...s-using-subwoofers.11034/page-29#post-1757805
I'll throw in my subjective experience. I have a single subwoofer crossed over at 100 Hz using a 48 dB/Octave slope. I do not detect its location when playing music, ever. Everything I hear sounds like it is in the soundstage presented by the speakers.