Stair for each of 3 `C130` types, will always float if placed in straight position.
In vanilla it maybe that wrecks are sunken into the surface, to imitate crash, which would make stair touch the ground, but from my experience it is hard to achieve positioning mentioned models in a way, that they would benefit from such stair placement. If you would lower the "plane nose", the chassis would not touch surface properly.
There is clearly more pros than cons for the community, if the stair piece was leveled with bottom of the tires.
If placed on straight surface (airstrip), it will look just right, if placed on a slope, stair may sunk a little in the ground, which will look like mother earth had just covered it with dirt.