Its pretty interesting from a couple of different angles:
1) GFO is an iron source, no matter what anyone tries to say to the contrary. Iron is an essential element for bacterioplankton growth. Putting an iron source and surface right at the same place as the carbon source is a good plan. Basically thats what Zeovit does as well, provides an iron-rich surface where the bacteria can grow. The question is, can the bacteria utilize the Phosphate that are attracted to the GFO?
2) The fact that the GFO is complexed with the pellet means that there is a slow exposure of the GFO and its Iron to the water. This prevents some of the issues with "Too much GFO".
3) The pellets simplify the balancing of the nitrate and phosphate with Carbon. In my system my nitrate is holding steady at 2ppm without direct dosing of nitrate any longer. I used to have to keep dosing it or it would eventually go to zero with regular pellets.
I think this is because the pellets balance themselves a bit:
a)Phospahtes too high, Nitrates too low, more phosphate binds to the pellets but there is not enough nitrate to grow much bacteria. Phosphate steadily removed.
b) Phosphates very low, nitrates high, pellets function more like standard pellets, growing larger amounts of bacteria and using any available phosphate for bacterial growth. Nitrate declines in this scenario.
Eventually these trend toward a balance where a small amount of nitrate and phosphate will be left in the system.
All my speculation based on observation and a lot of carbon-nitrate-phosphate experimentation over the last few years and now the last several months with the All in one pellets.