You don't have to dump it undiluted in the ocean. You can mix it with an outgoing treated wastewater stream if your system doesn't recycle it (or if you do recycle it then you have less need for more fresh water so your desalination plant can be smaller), or disperse it over a larger area for a gentler salinity gradient.

The real problem, as with anything, is the cost that would add. But if this technology can produce water for a negligible ongoing cost, that might be worthwhile.

This Practical Engineering video gives a great overview of the challenges and some of the existing solutions with desalination, including how to get rid of concentrated saltwater waste (in the context of reverse osmosis desalination, which this tech is kind of a hybrid of reverse osmosis and distillation).