Certainly no judgement from me, but I do not deworm. I've purchased discus from at least five of the Simply Discus sellers in the past 10 years and have not had any problems. Nevertheless, new fish always go into a strict 6-week quarantine, and I've not had any problems with this protocol.
I have had issues with discus purchased from other breeders and importers, mostly before SD came into existence. (Those were painful learning opportunities, which is why I always quarantine.) In each case, the problem has not been intestinal worms. I've read threads where people described treating with deworming medication and the tank was filled with worms afterwards (ugh). But I've never had a face-to-face discussion with any hobbyist about a personal experience.
I'm generally skeptical about powders you can buy over the counter, throw into a tank, to address fish diagnosis based on completely untrained observations. I know of no medication that does not stress out the fish and have had many, many experiences of watching fish die despite everything. Now when I see a sick discus, it immediately goes into quarantine. The heater is cranked to 93F and salt is added at the rate of 1 tablespoon/gallon. In every case, the fish will immediately look more comfortable. My preferred approach is to help the fish fight the disease on its own. (Note that this only applies to discus.)
Willie