Apparently it is low in cadmium, but how else will it better for the environment in regards leaching? It is still laden with nitrates.
I think you are buying into hype there, but happy to be proven otherwise.
Ripping up the seabed with little oversight, i.e. you can't actually see the damage I would suggest would offset any emissions caused by shipping by some margin. Then there is also the emissions created by producing the product itself. Do you know if they are more or less than alternative suppliers?

The ocean creates something like 75% of the world's oxygen, perhaps something we should consider before we start ripping up the seabed around the world. Or should we just keep pumping out carbon & reduce carbon filters and oxygen production?