I take your point about it being good exercise for the mind - quite so. But in the real world, if you rely on the database behaving in a particular way when that behaviour is not defined, aren't you asking for trouble? I wouldn't want code like that in a database I'm responsible for!
After all, for each new release MS will test that the database conforms to their definition of correct (hopefully from the documentation, or at least the same source as the documentation)!), not the way it used to work.