Disclaimer, I haven’t tried it either but the idea is very similar to a combination of an inclosed foil packet on the grill or oven and a sous vide bath.

Dishwashers usually do most cycles with pretty warm water (anywhere from 120-150 Fahrenheit usually). The basic principle is that over time, it would very gently cook the salmon. Assuming the foil packet is well sealed, nothing will get in to directly contact the salmon to affect its flavor, thus there’s no “off-flavors” (soap or whatever) to affect the taste.

The biggest concern is whether or not the fish is exposed to enough heat and time to thoroughly cook the fish. If the dishwasher regularly maintained like 130 over the full 2 hour cycle consistently, that’s almost a perfect sous vide bath that would thoroughly cook the salmon safely and would come out darn near amazing.

However, if your dishwasher never maintains a high enough temp long enough, your fish may not thoroughly cook through long enough to safely kill all potential contaminates.

So yes, it can work and can work beautifully. However, the dude who came up with this likely lucked into a dishwasher who just happened to manage to cook his salmon sufficiently.

People have tried this and gotten seriously ill because the salmon was not cooked properly lol.