Serious question: without carbs, what gives the beer any flavour? Obviously hops, but what else is there? Phenols? Esters?
A brew without residual dextrins doesn't necessarily have no malt flavour. Powdered malto-dextrin is actually quite bland.
Same for body, with the alcohol, surely the FG must be below 1.000? What does this do for body? How watery is it?
This depends on your definition of "body". Many dry wines are claimed to differ in body, which seems to be a function of fruit intensity, ethanol levels (ethanol is perceived as sweet at high enough concentrations), and congeners like glycerol, fusel oil, etc. On the beer side, dissolved protein, glucans, etc, can increase viscosity and therefore the sensation of body.
Just as there are carbs that yeast can't process (dextrins etc), are there any in the beer that we can't process?
Dunno whether it strictly qualifies as a carbohydrate, but cellulose and possibly other soluble fibres would be obvious possibilities. Mainly an issue with fruit beers, and most of it I imagine would precipitate. Lactose is another carb that yeast can't metabolise but which we can. Then there are always artificial sweeteners if one wants to play tricks, and even more cunning would be to add synthetic melanoidins and related substances if one could be bothered ...
As for how Burleigh do it, I would imagine dry beer enzyme would be a lot simpler than distillation (which is more appropriate for low-alcohol stuff). BTW, I've had their bottled weizen, and it's as good as it gets. A yeast culture is on my "to-do" list.
