Grounding protects you from problems with electricity that feeding electric devices. The hot lead in motor works its way loose and touches the case. Without ground there is no way for the system to clear the fault, and when you come by and touch the metal pump case - zap
Bonding protects you from differences in potential in conductive surfaces that may arise from who knows where. Maybe there is a defective underground feeder somewhere, maybe there is a cross on the pole and the MGN is now feeding the earth. Maybe your AC unit is causing the issue. Who knows, but bonding connects all the different conductive parts that you can touch at the same time, and makes them one big part.
So, if you pump is not considered a conductive part (because it is entirely encased in a plastic insulator) then it does not need to be bonded (in theory) because it is not a conductive item. Just like a set of plastic stairs don't need to be bonded a plastic (coated) pump does not need to be bonded (in theory) but everything else that can conduct electricity sill should be - pool water, earth, etc.
Bonding can be a little difficult to grasp at first. It seems odd - how can somebody be OK in the pool water, but if I stand outside the pool and touch the water with my hand I can be shocked. It has to do with differences in potential. In some cases with high voltages you can get shocked or killed by just walking. If there is a high voltage cross the difference in potential between two points on the ground can be enough to kill you. If a bucket truck makes contact with high voltage that can happen. The first choice is to stay in the truck (the tires are insulators), but if you have to leave (because often things start on fire too) you throw out an insulating blanket, jump onto it and then SHUFFLE away. Taking a step can bridge enough potential to send current up one leg and down the other.