Does anyone have a better source of info about this? I've found "good news" in the names of things to be a reliable indicator of people who seem to believe they're trying to make the world better while polluting the information environment as much as any other fake news site. I'd rate the article as slightly less credible than a press release from the company itself.
The thing is that you probably won't find anything that looks too closely at the efficacy of the claims, because the claims are all that anything is reporting on, since the product is so new. Here is a similar article published on asme.org (American Society of Mechanical Engineers), that discusses the buoys and the company's claims surrounding them: https://www.asme.org/topics-resources/content/tapping-the-ocean
If the water cycle shuts down to such a degree that the desalinated water is not making it back into the oceans, we have planetary-scale problems far more worrisome than a slightly elevated ocean salinity.
If you had an absolutely huge number of these in a small area, I'm sure you could probably create a localized disturbance in the salinity. But 13k gallons is a pretty trivial amount. That's a 50 meter cube of water per day... in the ocean.
I get what you're saying, but it's not like we're just taking that water and blasting it off into space. It's going to be used and then make it's way back into the ocean eventually. Either through evaporation and precipitation, or directly through rivers that feed into the ocean.
Of course, if there hasn't been already, there should definitely be some extensive studies into whether there are any blockades as far as that water returning to the oceans in a reasonable amount of time.