Or maybe it's just the perspective and they are stretched upward and not lying on the ground.
They are indeed reaching up. The lighting doesn't communicate depth very well, and the puffy jackets make it hard to tell how much of the change in width is perspective versus sleeve design. They're also off-model; their hands are the right size for being at their sides, resulting in Suzuka's hands being crazy tiny. Also Fate and Nanoha have long nails that aren't normal or practical for them, also Fate is going to be hurting in a second when Nanoha yanks her hair by moving, also Suzuka is clearly posing for a camera, also neither Arf nor Yuuno look remotely comfortable, also also...It's not Kouji's best work, is what I'm saying~