Good question. TTB does not require measurement of alcohol in beers but I'm guessing if the content is really 65% ABV and that is reached by freeze concentration, which they treat as distillation, that they would classify the stuff as spirits and require that the ABV be assessed by distillation followed by density measurement of the distillate. What this means is that the beer contains volatile substances which, when separated from the beer and mixed with enough water to bring the volume of the water solution to the volume of beer tested, result in a solution of the same density as a 65% V/V solution of pure ethanol. It does not mean that the beer contains 65% V/V ethanol but you can be assured that it contains nearly that much as few of the volatiles are more volatile than EtOH and thus come over with it in the distillation. One of those things is acetic acid but I doubt this beer has appreciable acetic acid content.