To me it looks like a victim of cost saving and overoptimization. Somebody requested that feature, and then someone discovered that if you hack around your sys

To me it looks like a victim of cost saving and overoptimization. Somebody requested that feature, and then someone discovered that if you hack around your system and set precise combination of fields, it will do the trick. So man hours were saved, some memo added to docs, and then the knowledge was lost. And all of that instead of adding separate form for specific case. I've seen it more than once.