This is not how DBS is done. The patient is conscious (and possibly performing some task) during the procedure of inserting the electrodes to ensure that they'

This is not how DBS is done. The patient is conscious (and possibly performing some task) during the procedure of inserting the electrodes to ensure that they're not positioned in a way that damages any critical functionality. The 'do you feel better now?' part comes when the signal generator hooked up to those electrodes is being tuned post-op. The article makes clear that it's the generated signal (maybe in combination with electrode placement, they're unsure) that's interfering with the ability to swim. Turning off the generator allows the individual to swim again. More fine-grained implants like neuralink can't come soon enough.