See:THE ABUNDANCE OF X-SHAPED RADIO SOURCES I.
VLA SURVEY OF 52 SOURCES WITH OFF-AXIS DISTORTIONS
The Quantum FFF solution is: that the BH plasma tail propulsion/repulsion ( pairing and splitting) trick only take place in space conditions without too much crowded BH space influences.
Conclusion: The merger BHs (see LIGO) are supposed to take advantage of the crowded BH space around Galaxy centers.
"Only Giant central merger black holes inside old galaxies".
The absence of a local single gravity direction for plasma tail steering behind the propelled BH, seems to create the the possibility to merge BHs instead of mutual repulsion as observed in X-shaped radio sources.
"This visualization of the 3-D structure of the Pillars of Creation within the star formation region of the Eagle Nebula (M16 below) is based on new observations of the object using the MUSE instrument on ESO’s Very Large Telescope in Chile. The pillars actually consist of several distinct pieces on either side of the star cluster NGC 6611. In this illustration, the relative distance between the pillars along the line of sight is not to scale."