Resting Pastry Dough Relaxes Gluten, Firms Fat
Rolling and shaping pie or pastry dough develops some gluten (even in a low-gluten dough) and warms the butter or fat worked into it; resting the dough in the fridge afterward lets that gluten relax so the dough won't shrink and fight back when rolled again, while the chilled fat firms back up so it stays in distinct pieces rather than melting into the flour. Skipping the rest is a common reason pie crust turns out tough and shrinks unevenly in the oven.
Sources & methodology: These tips draw on established food-science references —
Harold McGee's food-science writing, America's Test Kitchen /
Cook's Illustrated testing, Serious Eats'
technique reporting, USDA food safety guidance,
and peer-reviewed food-safety research (including UC Davis
cutting-board studies) — not reworded recipe-blog consensus.