Not 100% sure it will work. As understood (but this is not exactly clear from the description), the board uses the GPIO4 to provide the signal to the Raspberry for the shutdown. This imply that the GPIO4 should be set as input by their SW, so you don't have to use it in the Hydrosys4 hardwaresetting. From hardware perspective it should be ok as the GPIO4 is not used for special purposes.
Not 100% sure it will work. As understood (but this is not exactly clear from the description), the board uses the GPIO4 to provide the signal to the Raspberry for the shutdown. This imply that the GPIO4 should be set as input by their SW, so you don't have to use it in the Hydrosys4 hardwaresetting. From hardware perspective it should be ok as the GPIO4 is not used for special purposes.