I'm not entirely certain, so the majority of my opinion is derived from research and speculation. That being said, I think DB's kit has all of the microbes mixed into the soil with a little bit of the food. The other blends have a lot of food and a little bit of the microbes, so it's almost like a polar opposite in a lot of ways. DB's kit doesn't use a compost tea. The microbes are inside the worm castings, and 20-40 lbs of EWC is needed per bale of ProMix used.
Also, don't get too hung up on what most people construe as "synthetic" because with most complexes, they form naturally which then makes them organic. It's the complexes that have to be manipulated with acids or other chemicals or unnatural processes to form new complexes that is what is actually synthetic. That being said, the nutes in DB's bottles are organic as he doesn't use any of the exotic synthetics in his formulations.