CSX GP40-2 question

In the cab of a CSX engine, there is a sign that i saw, "Don't shut me down when im hot" why can't you shut the engine off when it hot, wouldn't you want it to cool down when it is hot?

http://www.railpictures.net/viewphoto.php?id=77463

If the engine is hot letting it idle gives the coolant more a chance to cycle through the radiator to help cool the engine and engine oil. A shutdown engines parts of course aren't being cooled by the oil because their not moving and may sieze, and cook the engine oil destroying it's lubricating ability. Any liquid cooled engine should be cooled down before shutting it off,
after it's been working hard and is hot.

oh ok, thanks