I’m quite interested in this too.
I think it would result in a much lower concentration of nematodes than the commercial solutions. Which I think is probably a good thing.
If in the natural state slugs have a 1/10 chance of getting nematodes, I’m speculating this would change the odds to 1/5 or so. Not enough to completely wipe out the population, but putting the gardener at a slight advantage.
I’m going to give it a try on one bed, with a control bed and will report back.