I'm upvoting this partly because it's by J. Kenji (Lopez-)Alt, whom I have regarded as a sort of culinary god ever since I first encountered his awesome piecrust recipe in Cooks Illustrated a few years ago.
(The piecrust is made by substituting vodka for much of the water, which allows the dough to be rolled out without encouraging too much gluten formation and thereby making the crust tough. It is perhaps a shade too much on the crumbly side but makes up for that by being outstandingly tasty, it has now utterly spoiled my taste for the majority of store-bought pies, and it has convinced my friends that I, in turn, am some sort of culinary god, even though this piecrust recipe is idiotically simple, actually simpler than regular piecrust, if such a thing is possible. The lesson here is: Subscribe to Cooks Illustrated and make your loved ones' lives better.)
I see that several of the commenters have run into the same problem that I did: If you use the full 1/4 cup of liquid the crust turns into soup. (It does, however, still work, which is a testimonial to how well the alcohol concept works.)
I tend to just leave out a bit of the liquid.
Although someone else in the comments suggests resting the dough for longer instead, perhaps even overnight. That might help soak up the full 1/4 cup. I tend to make this stuff in too much of a hurry, so my pie dough doesn't rest all that long.
A year or so after this recipe came out Alton Brown did his piecrust episode. I tuned in wondering (a) if the guy had done his homework; (b) if he could top the vodka thing for theatrical excitement. And Alton passed both tests by making apple pie with apple jack in the crust instead of vodka. Now that's theater.
So, I just did this[1], and my dough absolutely did not turn into soup, which has me concerned. Could it be a temperature thing? I keep my vodka in the freezer year-round; it pours like syrup. I chilled the hell out of my butter and shortening, too.
I'm curious whether it's the presence of alcohol that inhibits gluten formation, or whether it's simply the fact that 1/2 the moisture isn't coming from water.
[1] Hopefully, so I can stuff ginger-sage sausage, pork confit, and rice into it for dinner.
The original Lopez-Alt article merely claimed that the alcohol has a lower boiling point, and therefore all evaporates during baking.
Alton Brown's show went further, pointing out that alcohol doesn't just evaporate quickly, it also doesn't form gluten while it's around. I don't quite remember whether he also claimed that the alcohol actually inhibits the gluten-forming action of the rest of the water.
Clearly more data is needed. Or perhaps some primary-source citations, but they don't taste as good.
As for the soup phenomenon: It could well be a temperature thing, and I will put my vodka in the freezer next time and see how that goes. But it could also be a flour thing, I suppose. Every flour has a different protein content, every region has its favorite mix of flours (in the south, for example, you can actually buy the flour that makes Southern biscuits famously soft and tender), so unless we set out to use the same weight of the same flour we're going to tend to see different results. (My flour is King Arthur unbleached all-purpose, by the way. I'm not sure of the extent to which King Arthur is a national brand.)
He's a Cook's Illustrated writer? For his scientific approach to cooking I shouldn't be surprised but reaffirmed by my suppressed gut feeling: "Hey his articles are a lot like Cook's."
(The piecrust is made by substituting vodka for much of the water, which allows the dough to be rolled out without encouraging too much gluten formation and thereby making the crust tough. It is perhaps a shade too much on the crumbly side but makes up for that by being outstandingly tasty, it has now utterly spoiled my taste for the majority of store-bought pies, and it has convinced my friends that I, in turn, am some sort of culinary god, even though this piecrust recipe is idiotically simple, actually simpler than regular piecrust, if such a thing is possible. The lesson here is: Subscribe to Cooks Illustrated and make your loved ones' lives better.)