Ahh, I now understand the specifics of your claim. It appears you are correct that (prior to prohibition) one could produce alcohol and then intentionally add

Ahh, I now understand the specifics of your claim. It appears you are correct that (prior to prohibition) one could produce alcohol and then intentionally add non-drinkable substances that matched its industrial use and therefore not be taxed for producing drinkable alcohol. And, as you say, this doesn't establish anything specific to prohibition, such as an intentional ramping up of poisons. Which means the initial claim of the article still appears to be completely unsupported.