Quote from article: "Dr Courtine and Dr Bloch have developed a wafer-thin device with electrodes that could target the dormant nerves. Once implanted into Mr Roccati’s back, the device sent in pulses of electricity that mimicked those normally present in the nerves of an uninjured person as they walk.
By doing this, the device acted like an amplifier for any electrical signals coming from Mr Roccati’s brain. Those brain signals would normally be blocked by his damaged spinal tissue and be incapable of activating the nerves in his lower back. But with the stimulation device in place, Mr Roccati was able to voluntarily control those once-dormant nerves, allowing him to move his legs and walk."
It's his brain, the device is only used as amplifier. The fact that article talks about "Walk, swim, cycle" in its title is only a part of what people fitted with devices can do. It said he can also sit and talk to friends at bar.