I think I may have misunderstood the manufacturing process. To my reading, it looks like they have 3mm-thick wafers, accumulate a 20mm-thick layer of hydrogen, which then shears off in a furnace, leaving...a 3mm-thick wafer. Which they started with. Thanks in advance to whoever explains how I've misunderstood this.

EDIT: Oh, I neglected to pay attention to units. The above should be 3mm, 20-micrometer, and 2.98mm, respectively, which means the sheet shearing off is 0.002mm thick. This is seriously cool. Thanks for everyone's patience.