Just as the title says. I read this comment and it struck me as ridiculous as first, but then I recalled reading articles on how many laws in the US are passed nowadays without legislators fully reading them, and began to wonder if there is anything to support this?
While I am by no means an expert, I can at least attempt to answer some of your questions.
Prior to the Civil War many northern and midwestern states legislated Prohibition. But with the end of the Civil War the movement for Prohibition faltered and drunkenness became a huge social issue.(Mennell, 160) To look further into this is the belief that this was a disease, noted as being "Peripheral Neuritis" or the alcoholic.(Reynolds) The Anti Saloon League, formed in 1893, led the charge for the third round of Prohibition legislation, from about 1907 with Georgian legislation furthering the cause. Years later (by 1913) the Anti Saloon League began to drive for National Prohibition and with their pressure on Congressmen as well as the First World War, began the passing of larger legislation.
In 1917 both houses of Congress had voted the 2/3 majority to send to the States a ratification for the prohibiting of the manufacture, sale, transportation, import, or export of intoxicating liquor.(Levine, 463) In November 1918 the War Prohibition Act was passed which banned the making and selling of beer and wine that had more than 2.75% alcohol. With the specific numbers mentioned here, and given that the average beer and wine, of the time and present, has greater than 4% alcohol, it seems clear then, that most politicians would understand that this would directly affect beer and wine production.
In 1919, with the Volstead Act the determining factor of whether or not something was 'intoxicating' was that it had greater than 0.5% alcohol content. With the passing of this act the government had to know what it was doing, including the banning of beer and wine, given the specific nature of naming beer in many of the acts that came prior and subsequent to the passing of much of this legislation. At midnight on January 16, 1920 Prohibition came into full effect within the USA.(Mennell, 162) President Harding expressed in a speech in Denver (1923) that the Prohibition Act would never be repealed.(Tomkins, 16)
So, with what we know about the legislation and its particular and specific nature about alcohol content and by name damning of beer and wine, it is fairly safe to say that, like now, some politicians didn't read the legislation. But given the obvious nature of the law, being a constitutional amendment, and it's far reaching implications, especially that beer and wine would be included, that a good many of the politicians understood the consequences of their votes.
Sources
Levine, Harry, and Craig Reinarman. "From Prohibition to Regulation: Lessons from Alcohol Policy for Drug Policy." The Milbank Quarterly 69, no. 3 (1991): 461-94.
Mennell, S. J. "Prohibition: A Sociological View." Journal of American Studies 3, no. 2 (1969): 159-75.
Reynolds, Ernest, et al. "A Discussion On Peripheral Neuritis In Beer Drinkers; Its Precise Causation And Diagnosis." The British Medical Journal 2, no. 2128 (1901): 1044-049.
Tomkins, Floyd. "Prohibition." Annals of the American Academy of Political and Social Science 109 (1923): 15-25.
Just a personal peeve of mine:
Just because legislators might not read their bills doesn't mean they don't know what they're voting on. They have staffers to judge local effects, their caucus has policy experts, and they get enough information to be much better informed than the typical "politically-minded" reddit commenter. They may not open the bill and read the exact text, but everyone has at least read a summary of the effects the bill will have.