Mr. Pemberton pretty much nailed it IMHO,
I would add only one thing. In addition to breaking the oil bond, such that one would not have to resort to then hard to remove solvents, the olefin specific formulation allows the cleaner to break that bond with a lesser amount of water. Using minimum moisture is important to cleaning olefin, such that the potential for wicking is minimized, if you hope to do so without post-padding.
The use of an olefin specific prespray is also best served with the right emulsifier in the rinse process as well. The high performance surfactants evident in olefin presprays often have a high HLB value, in that they are stronger oil emulsifiers than water couplers. Therefore, again to minimize the opportunity for wicking, it's best to select a rinse agent which will move the soil/prespray emulsion AND excess surfactant out of the carpet, with the least water possible during the rinse/extraction phase.
I often pair the olefin prespray with a good rinse product like the ones I mentioned in the preferred acid rinse thread of Jimmy's a few days ago. I know a lot of people really are proponents of post-padding and dropping airmovers on commercial olefin, I and I do think that they are good ideas. However, not everyone has the equipment to do so (or the built-in profit margin to absorb the cost of using enhanced drying methods). If that is the case, then the right combination of chemistry and technique can still work, while avoiding wicking.