It appears that back EMF from the woofer is decreased or almost eliminated when diagonally connecting.
It may be microscopically affected by changing speaker post connections, but only to the degree that the connection resistances change to the various generators of EMF in the speaker.
By moving the cables you are either adding or reducing temporary connections in the signal path, which affects damping.
If the cables were formerly connected to bass terminals that is the least resistance connection to the largest generator of EMF in the speaker, so the amp sees the highest possible EMF. Now if you move the negative cable to the tweeter, the circuit is still the same, but you have reduced the amps connection impedance to the tweeter, and you have increase the impedance to the woofer by moving the resistor (the temporary connection speaker post) from the tweeter circuit to the woofer circuit. The tweeter's damping (detail) increases, and the woofer's damping (slam) is worse. But this also means the woofer's ability to preturb the amplfier with backEMF is also reduced slightly, but not by much, because you still have a voltage source amplifier with a low output impedance that conducts the VC-generated current, and you still have lowish impedance connections from VC to amp. Nothing has changed very much technically, which is why this tweak is a secret, but small changes are audible.
To eliminate backEMF completely, you need a current source amplifier, which has infinite output impedance, showing an open circuit to the VC, so no EMF current can flow. Like First Watt F4, but this kind of amp has special needs and won't work with normal speakers.