Dunno if those are real specs of the case cause the phone itself has similar specs. iPhone 5 specs directly from Apple:
Height: 4.87 inches (123.8 mm)
Width: 2.31 inches (58.6 mm)
Depth: 0.30 inch (7.6 mm)
Weight: 3.95 ounces (112 grams)
The case would be like using Saran Wrap.
They all seem doable. The length is really close but maybe wanted to really make the slimmest water proof case like they claimed at ces