That's probably worse because that seems like a pretty basic rule.
So is being in the end zone on your own impetus for a safety to be called. How more basic can you get?
The safety call was simply seeing something wrong. Every official makes those kinds of mistakes. Usually not by 5 yards, but nonetheless, it's the same thing as seeing a safe runner a out. This case, a basic rule was applied incorrectly. There's no excuse for officials to not know such a simple rule.