You forgot the case 5) ports match, some protocols match, port works at much reduced capability.
This is great for backwards compatibility, but can confuse users. You could have a TB3 drive attached to a TB3 computer by a USB cable with type C connectors that only operates at USB 2 speeds. It will silently fall back to a very slow transfer.
I don't know how the committee could have done much better though; this kind of fallback is important. Some mandated labeling would have helped a lot though.
This is great for backwards compatibility, but can confuse users. You could have a TB3 drive attached to a TB3 computer by a USB cable with type C connectors that only operates at USB 2 speeds. It will silently fall back to a very slow transfer.
I don't know how the committee could have done much better though; this kind of fallback is important. Some mandated labeling would have helped a lot though.