*edit:* ~~ah..hmm..
its to do with animated mesh/colliders, that can intersect either the ground colliders in KSP, or that extend ouside and mesh with the bounds of the craft that KSP calculates...
I dont know if its intentional, or not, but KSP spawns the craft that high, so the craft doesnt explode upon spawn when the part collider intersects the ground collider.~~ -> ah..hmm..
its to do with animated mesh/colliders, that can intersect either the ground colliders in KSP, or that extend outside the craft bounds, that KSP calculates...
I dont know if its intentional, or not, but KSP spawns the craft that high, so the craft doesnt explode upon spawn when the part collider intersects the ground collider.