What does this mean?

Most High quality interconnects do have three conductors and it's only a matter of installing XLR's to use them in a balanced system.

Another item of importance is that the sheild should not be connected at one end and not the other. This can make the cable act as an RF antenna.

Rwwear has it right. Audioquest could be the culprit of the confusion (no offense to AQ--I do like their cables), but they did a long line of "triple balanced, RCA or XLR connections" they also had a previous line of "double balanced" Then they changed to calling them "X3" version rather than triple balanced, probably due to this confusion. The balanced aspect referred to the wire. But as stated to get true balanced functionality you need the XLR connection.

well almost right---
shields are terminated at the signal-originating end only to prevent ground loops. If terminated at both ends the shielding effect is degraded significantly.

Not True. If you are not going to terminate the sheild at both ends you shouldn't terminate it at either in an unbalanced system. This doesn't mean that you will automatically have RF problems if you do not comply with this rule, but you can.