When I was an electrical apprentice, I could not wrap my head around it. That is, until my foreperson sent me to see why a 3-way switch wasn’t working. That was a day!

In the diagram on the link they are using a three conductor cable after the first three way switch. Black, Red, and White with a separate ground.

To make the wiring work flawlessly, so your husband becomes a lover of these switches, you install the same special three-wire cable between all the three- and four-way switches in the circuit.