My reasoning is that if the wreckage had fallen like a stone, straight down along the y-axis, the impact with ground would have been more severe. A crater of some kind, more damage to the outer parts of the wings.
This demonstrates a flawed understanding of the real physical characteristics of an airliner. "Like a stone" is a complete misunderstanding of the relative density of a jet plane or its components. Instead, the average chunk of a jetplane is mostly air. It will not fall like a stone. Instead, it falls like a nearly empty cardboard box.
Barring an intact nose-first impact at very high speed, like 9/11 United 93, or the ValueJet 592 Everglades crash, which are clearly not the case here, the only chunks that are even capable of "cratering" typical soils are engines and landing gear.