The constantly changing units of consumption, historical timing, changes between daily and annual rates of consumption and similar made it difficult to understand exactly the point that was being made.
The author dug up a lot of data and put it together, but didn't going the extra step of unifying things in a way that's easy to understand.
I kept having to convert the units they were using to units I could understand, and since those units weren't constant, it's difficult to get an overall impression.
But, a few examples I did convert to amounts of drinking I understand:
* In Florence in 1455, someone (IDK if this is an average, an individual, a certain class of people or what?) drank 250L of wine in a year. That's about .9 modern size bottles of wine per day. A good amount, but I expect if you were practiced at it and drank it fairly evenly throughout the day, you certainly wouldn't appear drunk.
* In the medieval city of Ghent, the apparent average per person annual consumption was ~40-liters wine and ~1300-liters beer. That works out to basically 7.5 pints (16oz, or the size of one of the tall cans of that craft beer often comes in in the US) of beer every day, and a quite small glass of wine. Depending on how strong the beer was (doesn't specify if this was small ~5% or strong ~12% beer), I expect even a practiced drinker would be quite tipsy after close to 8 pints and a touch of wine every day.
* Sailors got a ration of 8 pints of strong (13% ABV) beer a day, which would have me absolutely knocked off my feet. 3 pints of what I think of as strong beer (~6-8%) in any kind of close succession and I'm definitely feeling tipsy, and shouldn't be let anywhere near something so complex as rigging. Though, after reading a few books on naval life aboard 16th century British sailing ships, perhaps being totally out of it for as much of the journey as possible would be a solid survival tactic.
* The "historical average" (IDK what period of history, or how average) beer consumption was around 380 liters per person per year. That's just over 2.2 pints per person per day. A long way from "being drunk all the time", even if it was higher ABV strong beer (and it certainly wasn't all high ABV).
Certainly, people seemed to have drunk much more in the past than they do today, but it's hard to make clear conclusions when the units are all over the place.