Neem oil flush vs spray recipe

[Jim S]

I’ve seen a lot of recipes for using a neem oil spray on leaves, but nothing for a neem oil solution to be used to flush through potting medium.

I recently found some sort of bugs (type unknown) on a tray after flushing potting medium with plain water (there is no evidence of bugs or damage on leaves). I used the AOS recipe of 4 teaspoons neem oil, 2 teaspoons dish soap, and one gallon of water, then poured the solution through the potting medium. Is there a reason why a neem oil flush isn’t mentioned as a treatment option?