Well, just to be scientifically accurate, one could do very high plate repeated distillations on a top quality fractionating still, and eventually should be able to get something as pure as you would get from activated charcoal filtration, so long as the contaminating material is not a strong azeotrope with ethanol and water. Most are not. And it would certainly not be a cost effective way of doing this. But perhaps what you heard is what I heard when I was having my discussions about classifications of GNS as base spirits for redistilled gin, because I thought I had heard the same thing somewhere along the line. Yet Denver's point is still nominally correct: unless they test or inquire, how will they know? Without a required formulation, they would not know that you did not charcoal filter, unless you are doing vodka only and your DSP application does not include filtration in the process description? And I fear if they did inquire it would just come down to this: if you did filter, they would leave you alone, but if you did not and there was any reason to suspect you did not meet the requirement, they could just say you didn't meet it. Hmmm...