This would definitely speed up the transfer. The external drive should be connected to the Mac/PC to avoid sending the data twice over the network. As a Nucleus is a small device, it should be possible to move it temporarily if needed to place it somewhere where wired Ethernet is available.
Note: 6.5TB won’t get copied in an hour. I would expect something around 16 to 18 hours over Gigabit Ethernet if all works well.