It does look like a toilet. I wouldn't get it, I don't think it will sell. It may or may not work, perhaps the water doesn't really go all the way through the soil, maybe just through the bottom part or something, IDK.
i have something similar to that running on a turtle tank
basicly you are growing plants the same way a heavily planted tank has no nitrates, except the plants arent going to be in the water.
yes plants need all those other nutrients but some plants will be hardier and some of those nutrients will be provided by fish food/poo.
there is still a stocking limit (which the turtle surpasses haha) to keep the water still low in nitrates.
There are similar plant filtration systems utilized already. A mangrove sump system is used by some dedicated hobbyists to eliminate nitrates.
The one huge disadvantage I see with this design is that you cannot clean it. At least with a traditional filtration system, you can lightly wash off the filter media.