I bought a small dehumidifier for an upstairs room that gets too humid. I pour out a gallon of water from the machine every 24 hours. How pure is that water? Is it like distilled water?
Ideally it would be, but it will pick up dust and other impurities from the coils it is condensing on. And since dehumidifier water isn't meant to be drunk the manufacturer doesn't have to follow the same rules it would for food-safe usage so can do thing like use lead solder which it couldn't on water pipes.
That’s how distillation works.
The only caveat to an instant “yes” is, as noted, surfaces and atmospherics may introduce impurities as the manufacturer did not intend the purity of the results.