I don't think you misunderstood foggy's question.
Foggy is asking about the color coding of the wires, specifically using a white wire re-identified for use as an ungrounded switched conductor in a three way switching circuit.
The quote that you posted speaks to illegal three way switch circuits where the grounded conductor was switched. The simplest example would be one where you have two switches at two locations, each with a supply grounded and ungrounded conductor and a switched conductor feeding the lamp. Both supply leads are connected to the _traveller_ terminals, and then a conductor run from the _common_ terminal to the light fixture. With two switches you have two conductors, and depending upon switch position either conductor could be grounded or ungrounded. If both conductors are grounded, the lamp is off. If one is grounded and the other ungrounded, then the lamp is on. If both are ungrounded, then the lamp is off again, but electrically live.