Redsy, and Walrus, you both bring up good points- which I ignored earlier for the sake of simplicity.

Some products -like the Crouse-Hinds product Redsy linked us to- are actually a powdered metal suspended in a light oil. When the oil evaporatesm there remains this powder, which continues to provide grounding continuity, as well as prevent the threads from rusting together.
I still have problems with the use of it in a hazardous locations. Absent other complications ( severely corrosive location, stainless steel joining aluminum, etc) I would rather not use it there.

Walrus brought up corrosion. As I see it, the Haz Loc requirements take precedence over the corrosion issue. Still, it is something to keep in mind. Unfortunately, equipment is generally designed to meet ONE environment at a time!

Just because something is UL listed does not necessarily make it suitable for all applications. Competing products, which appear equivalent, may not all be appropriate for a particular job.

A final caution: let's try not to get confused by terms. Fitting threads together does NOT make them "dry seal" threads. "Dry Seal" threads are a type of pipe thread with specific dimensions that are intended to seal without the aid of any tape or lube. The NEC requires us to use NPT threads in the field, which have an entirely different set of tolerances. Even though they can "fit" together, they're not the same. (Machinery's Manual has the details).