I actually don't think that's true. They met through work, but didn't start dating until her summer term in the job ended.
"Robinson met Barack Obama when they were among the few African Americans at their law firm, Sidley Austin LLP (she has sometimes said only two, although others have noted ut there were others in different departments).[55] She was assigned to mentor him while he was a summer associate.[56] Their relationship started with a business lunch and then a community organization meeting where he first impressed her.[57]"
How many great relationships/working relationships wouldn't be ruined because of that rule?
How many people wouldn't have lives and careers ruined because of that rule?
Frankly if you love someone that damn much, move to a different job and avoid the potential conflicts that are involved. Good luck arguing that a boss absolutely needs the option to date a subordinate because what if a serious relationship never happens?
I mean it's nice if you can pull examples out of the air when it worked out for two people. But for everyone else? What's the ratio of happy couples to victims do you need to tilt scales to one side or the other?
This is completely absurd. How many current great relationships would have never existed under such a rule? (Bill and Melinda Gates is the obvious go-to example, or Barack and Michelle Obama, but there are no doubt millions.)