When making ciabatta, why must the proofed dough be flipped over before being dimpled and placed in the oven?

Hello again. I noticed that some ciabatta recipes (like Craig Ponsford's, in Artisan Baking Across America) require the dough to be proofed seam side down, then flipped over onto the peel seam side up, then loaded into the oven. What would the difference be if I just put the dough in the oven without flipping it over?