Sorry but there ain't no yeast that can ferment to 67.5% so that means it's just a high test whiskey with some beer in it and that ain't beer! It's beer-flavored whiskey.
I am pretty sure they manage to get this high mostly with yeast. It's possible the freeze concentrate it at some point but you can get a really really high ABV with progressive feeding along.
start out with 1 gallon of 1.090 or so wort, when that has attenuated out most of the way add another gallon of 1.100 wort, this will result in a gravity somewhere in the middle 1.050ish. that's easy on yeast. it attenuates most of the way and you hit it with a gallon of 1.200 wort. at some point the yeast will die form the alcohol, and I am sure it's well before 67.5 percent but might well be upwards of 20% as there are wines that are close to that. so at that point you have to remove some water to get the rest of the way. enter eisbeir.
Most of the time what will hold the yeast back is the high wort gravity and resulting osmotic pressure rather than the high beer ABV.
but anyway. If someone offered me a sip I'd taste it but I agree. it's not really beer.