> Ethernet has had the concept of full duplex for several decades and I have no idea what you mean by: "hybrid on each end allows the use of the same channel at the same time."

Gigabit (and faster) is able to do full duplex without needing separate wires in each direction. That's the distinction they're making.

> The physical electrical connections between a series of ethernet network ports (switch or end point - it doesn't matter) are mediated by CSMA.

Not in a modern network, where there's no such thing as a wired collision.

> Take a single switch with n ports on it, where n>2. How do you mediate ethernet traffic without CSMA - its how the actual electrical signals are mediated?

Switches are not hubs. Switches have a separate receiver for each port, and each receiver is attached to one sender.