Jitter isn't caused by cables. Its caused by the devices either side.
Typically on switches or routers, where packets are received on two different interfaces, and need to be transmitted out a third. If two packets are received at the same time on the two ports, one of them must be queued while the other is being sent. This will introduce a small amount of jitter. This is magnified with a busier network, and is one of the things QoS tries to eliminate for certain traffic types (typically voice on enterprise/ISP networks).
The most a cable could really do is cause a packet to get mangled, and retransmitted. I suppose this could be viewed as introducing jitter, but its at a higher point up the stack at the application layer, rather than the network.
I find it amusing that the guy in this article completely glosses over the importance of the switches in his network. If he had any other traffic running over his network when performing his tests, they are pretty much invalid.