Much better explanation than my off the cuff attempt, great added detail.

Salt brine is highly corrosive to anything in contact with it so it is difficult to move, and in high concentrations wreaks absolute havoc in surrounding ecosystems. There’s a reason the phrase ‘salting the earth’ doesn’t have a good connotation. Desalination on a small scale might not seem like an issue but when dealing with the waste at scale becomes a bigger issue than even the energy cost to perform.