I think the theory would be that the first time packing is exposed to product, it will swell slightly. If the packing is installed dry and given an initial adjustment before it is fully saturated, it could swell slightly resulting in inadequate leakage and the possibility of burning up or glazing over. Especially with Teflon packing, once it is glazed over, it will never seal properly again, no mater how it is adjusted. I probably came across as harsh with my first reply directed at Artisi. On further thought, I might state my case differently.
There is no doubt that a skilled and experienced person can install packing dry (or coated in grease) and get excellent results. It may involve a very careful packing technique. It may involve a period of operation and adjustment at various times after start-up. But, in my experience, these skills are harder and harder to come by. And spending the time to make multiple adjustments over time is harder and harder to justify. It may be that packing that was soaked before installation could be installed with slightly less skill and less adjustment during initial run and still achieve very good results. Perhaps it is saying that you could get about the same outcome, but get it faster and cheaper with a less skilled workforce. And, I include myself under that category of less skilled. I have personally packed our largest water pump with Teflon packing that had not been soaked and had the packing smoke on start-up. Installing packing is one of those things that is harder to do well than it first appears. And, by soaking the packing before installation, I have been more successful with less time and effort.
Johnny Pellin