Well not necessarily--everyone has their own opinions. While you do not need to go with 5 gal buckets or totes, I can guarantee you that you cannot take 6 plants to harvest in a single 5 gal tote. The dimensions of that tote are about 16 x 12--about the same size as 2 pieces of paper. I think that if you lay out 2 pieces of paper and try to imagine 6 plants in that space you will see that it is just too small.
I have 5 totes that size that I do use sometimes, but I only put one plant in them. I have a couple of 10 gal totes that I will put 2 plants in, but only if they are somewhat small and the same strain for even with a 10 gal tote their is limited room for the girls to spread their limbs.
You do not necessarily have to use 5 gal buckets, any plastic container that does not let light through will work. You just want it large enough to hold enough nute solution so that you are not running dry in a day or 2. I have found even 3 gal a pain to work with. Remember that you cannot fill with nute solution to the top of the tote. I also like to use individual totes so that I can raise and lower plants to maintain an even canopy. I also have plants that like different concentrations of nutes.
That system could get you started and you could probably veg in it for maybe 3-4 weeks. You would need to check your nute solution a lot to make sure you don't run dry. You would have problems if the plants grew at different rates, however. If you want something like this, you should make it yourself as you could probably make it for under $20. But like I said, this would just be for a little while, while the plants are small. You would ultimately need something larger to finish.