But all of the current of all frequencies travels on the single wire from the amp circuit to the amp terminals.
And do you use speaker wire with magnetic shielding to prevent magnetic interaction between the two wires?
And to my other question, what about the current at 4kHz and 8kHz travelling on the same wire?
Also as a driver is a coil inside a magnet, when a driver moves backwards it creates its own current that travels back down the cabels. Removing the post jumpers and bi-wiring back to the amp terminals reduces the chance of the backwards current to interfere with the other driver, as the amp itself is more capable to dampen the return current.
Removing the post jumpers just moves the point of electrical connectivity between the paths to the LF and HF crossovers to be at the terminals of the amp instead of the terminals of the speaker.
Any capability that an amp may (emphasis on may) have to dampen a return current would be moot because the return current would just happily head down the other wire from the electrical connection at the amp terminals.
Assuming you have used sufficient gauge wires on both sides of your bi-wire then the amount of return current arriving at the input of the LF crossover that the tweeter generated and sent back down its wire will be exactly the same whether the point of electrical connectivity is the speaker terminals or the amp terminals.
You have just made the same logic error again by ignoring the current difference and focusing on signal. You say there is no difference because there is no difference in signal. But that is ignoring the difference in current.
But there is no science to explain how the amount of current at any frequency between the crossover and the driver would be any different in either situation.