This may be a definitional problem, but assume the transmit coil is several meters away, and the two tanks are at the origin, mounted at 90 degrees to each other.
The frequency is low, so at this distance we are inside the radiansphere, and inverse cube law applies.
If the transmitter is at an angle where each tank is pointed 45 degrees off to the side of the transmitter, (transmitter bisecting the angle between the tanks), then that more or less copies the real world situation.
Physically, the ends of the two inductors are, and must be, located very close to each other (single digit mm) I can't change this.
So you say that "the transmitter does not couple exactly identically to the two tanks"? If we adjust the angle so that each tank is the same angle to the transmitter, then the intensity and phase of the signal arriving at each tank should be identical, except for the signal radiated by the adjacent tank.? Agreed?
