It doesn't stop them. But when the plants reach the 3rd level of health (which most people have never seen) the plant changes from mostly carbohydrate structure to more protein and when the pests eat it, it ferments in their guts and kills them. That's why I no longer have bean beetles or potato bugs.
The brassicas have been the lone holdout, something I'm not yet doing hasn't brought them to this level. Flea beetles are far less now but the tiger moths and white butterflies still take a toll. I'm getting there...
Interesting and good to know! I'm into trying to build really healthy soil to have good healthy plants, bit by bit.
I tried the guess method for many years. Once I started comprehensive soil testing, I found out I'd actually been making the problem worse. Once I started putting down what it really needed, many problems started to disappear. I could only do it bit by bit, as there wasn't much money through that period.