Putting all technicalities aside, this is all you need to know. These days, we use higher fuel pressure to raise the boiling point, but earlier fuel injection system commonly looped fuel around in a circle so that fuel doesn't boil and cause a vapor lock in the fuel rail from engine's heat.
A-B = fuel consumed by engine, this is what you put in your gas tank and what you pay for.
A=fuel flowing to rail.
B=fuel returning to tank.
You could say that power factor is comparable to (A-B)/A
Say you have a power factor of 0.5. When you consume 10 gallons of gas, the fuel filter and fuel pump will have to handle 20 gallons of gas. If you have a power factor of 0, the gas is just going around in a circle but none is consumed.
The A line can only carry so much.
Say that the fuel pump and filter belong to the power company. If you have a poor power factor, you're charged a penalty for wasting power company's resource by using excess amount of "A" path's capacity IF AND ONLY IF YOUR BILLING SCHEDULE IS STRUCTURED AS SUCH. Residential customers are not on that schedule.
If you put a recirculation pump and a radiator between A and B right by the fuel rail, the amount of gas going back to the tank will become zero, but the amount of gas you'll have to buy won't change. This is beneficial if you're surcharged for the amount of fuel that flows through the filter. If you're not, its useless.