it is worth pointing out that on the list of motors from the xrc control (shown above) there is yaskawa part number SGMG -13AWA-YR*
this motor is not one with the typical motoman connectors on it. it has a 15 pin JRC connector, and a 7 pin or so connector / also mil spec style. the first one (15 or so pin) is the encoder output. the other is 4 wires for the motor, and 2 more for a brake. yaskawa also makes this model with no brake so it would be a 4 pin connector in that case.
having had a look at the sgmg servo datasheet, there is no pin for serial comms to the encoder. its just standard encoder output. a+ a-, b+ b-, and so on. nothing to where the xrc control could poll it about the configuration / motor type.
it is also worth noting that this servo motor has exactly the same current and voltage requirements as my 'non yaskawa' linear motors made by anorad / with renishaw encoder of my choosing.
seems to me that i can hook up that motor and it should work as its in the list of motors from the robot.
also seems to me that i can just hook up another motor with the same specs and pinout, and it should just work too.