'Gardenburger' is a brand name, but has also come to be a generic product term for all veggie burgers, similar to Kleenex for facial tissue. Unfortunately, in the case of Gardenburgers, this leads to some confusion.
Gardenburger™ makes both of the two fundamentally different types of veggie burgers. One type is just plan Gardenburgers™ which are patties made from rice, beans, TVP, various other vegetables and sometimes cheese. While being tasty low fat patties to put on buns, they are NOT simulations of ground beef hamburgers in terms of taste, texture, or protein content.
Gardenburger™ also makes the other type of veggie burger, in the guise of 'Hamburger style Gardenburgers™', made with soy protein, which ARE simulations of beef hamburgers in terms of, taste, texture, and protein content (with a lot less fat and e-coli of course). While these are nowhere near the highest quality hamburger simulations (Harvest Burgers™ have a far superior taste and mo' protein), they were among the first.
So, a Gardenburger is just a brand name, and it can be two fundamentally different types of patties. Sometimes the name 'Gardenburger' is misapplied to just the first type of veggie burger, and sometimes it is misapplied to all veggie burgers.