Whatever happens to a Ball by accident, must be reckoned a Rub of the green.
So a ball that lands in an unrepaired club mark left when a golfer took a divot is accidental. Even if the golfer's intent in leaving the club mark unrepaired was to penalize following golfers, the odds of a folowing shot landing that spot are very long, so an unfortunate landing there should be considered an accident.
Now a stymie, on the other hand, is different. One player certainly could stymie another by accident, but some golfers played for the stymie deliberately. So to me modification of the stymie rule makes sense.
In a perfect world, every golfer would repair club marks, and apparently that will happen before people stop calling them divots.
Full disclosure: I probably would feel differently about this if I hit more fairways.