We called it situational ethics, but you are right, it has been around a long time.
There is a time and place for situational ethics. For example:
Q: Should people obey traffic laws like speed limits?
A; Yes
Q: Suppose your father suffered a heart attack late at night and you were taking him to the hospital at 3:00 AM and there was no traffic on the road. Would you still drive the speed limit and come to a complete stop at a 4 way stop if there was no other traffic?
That is a situational ethic. It is useful because it lets you know the intent and limits of the law in regulating moral behavior. If done right there is nothing wrong with thinking through that type of situation.
The problem with these exercises is that they are encouraging you to objectify humans by usefulness. They are not focused on personal choices but upon forcing those choices upon others. They always seem to fall back on some sort of Social Darwinism to derive an answer.