Connected?
I guess we have to define terms.
The digital FBW systems have a basic time frame/sample rate. So dual controls that feed the inputs to HAL are sampled at "x" rate, then used by the system.
The pioneer system I flew back in 1979 was analog. The force inputs on our controls was used by four computers, and the most benign output was used to command actual surface movement/rate/etc.
In our family models, the control signals were "summed", so I could equal the force that the nugget in the front seat was exerting. The FBW used the resulting electrical signal to command control surfaces.
So I would prefer the term "mechanically-coupled" to discuss those planes with dual controls, regardless of whether they are FBW or the "conventional" implentation many of us grew up with. out,