I got the same email and ended up buying one.
Actually the tank is fine - it follows the 1"/gallon rule. And you can buy the system with or without the heater - I already had a heater from an older shrimp tank, so I didn't need one. I did buy the little LED light though.
Marimo Balls do great in smaller tanks like this, it would actually be more beneficial to have one in the tank vs. not have one.
From the photos they have, the media they are using is a coir based hydroponic media, so there is a lot of surface area. I liked the fact they are marketing this for succulents vs. vegetables, it should do well for filtering the water.
For the price, the little starphire tank is worth it in itself.