I tend to work on logic, so here's what I see happening during your one-time experiment.

Most clothing that isn't heavily soiled or stained will clean fairly well in water alone - with or without detergent/soap or soapnuts. My SIL had to do this for a period of time due to a skin condition and was surprised her clothing didn't look much different than when she used laundry aids.

Since you added CS as a prewash, that probably did it's normal job cleaning the laundry.

I read this online about soapnuts:
"Note: While good for normal washing, soapnut isn't great on really stubborn stains (red wine, grass, blood)... Warm water is also needed for maximum effectiveness in order to help release the saponin; the higher the temperature, the more saponin is released."

It appears the soapnut shells contain saponin (the same stuff I rinse off my quinoa before I cook it), usually present in quantities of around 10-15%. Saponin dissolves in water to form suds and can dissolve fats and oils and help to lift grime. I believe plain old hot water will do that, as well.

At least it's an interesting concept....

-Grainlady

Grainlady, I kind of knew all that,I just wanted to try them. I thought the nuts would be bigger and somewhat softish-almost maybe some moisture in them.Sort of like dry dates. Maybe I got really old ones.
I was even surprised when I put then in the hot water in the cup, it didn't feel soapy at all not sudsy, just dark water so I did dark load and used the CS just in case.
I was hoping for someone here to have some input on them. On line people seem to like them. Thank God I only got few samples.