Pat's answer was well thought out and informative. And Larry's comment was, well, what we'd expect.
To add one more aspect to the fine description that Pat gave... Carpet has a tremendous ability to hide soil. Carpet consists of fiber and space. Displacing soil from the visible surface in a dilution of encap detergent and moving it out of view is what's actually occurring. That's why the carpet "looks" clean right after it's been scrubbed - even before the post vacuuming occurs.
Then as the carpet dries the soil that's suspended in a good crystallizing encap detergent can be extracted through the post vacuuming process. Keep in mind that the fiber is flexible, so a brittle polymer is naturally going to shear from the fiber as the fiber flexes. That's why the next vacuuming, as well as with subsequent vacuumings - more and more soil will continue to be recovered. Yet the carpet will look clean initially without vacuuming.
Since a good polymerized encap detergent is not sticky like some traditional detergents, there's no soil attracting residue left in the carpet. Instead the carpet will resist re-soiling. This further underscores the need for having an encap detergent that contains a good quantity of polymer. In fact, the reason why many so called encap products fail to perform well is because their formula contains little or no polymer. Encapsulation polymers are costly. By comparison, the other ingredients in a detergent are much less expensive. That may account for the differences between some of the encap products performance.
Releasit products are loaded with an Encap polymer that serves three roles: (1) It does a very effective job of capturing soil, even oily soils. (2) It releases from the fiber readily so it can be recovered with vacuuming. And (3) It resists resoiling.
Hopefully that helps explain the mechanics of what's going on a little bit for you. Feel free to call me too, and I'll be happy to try to walk you through it. 800-330-1888.