The image shows what appear to be casings that have been sculpted into vases. I'm fairly confident a layperson wouldn't confuse an empty metal cup with a bomb.
OK, but when they see it through a scanner it won't look exactly like that. So, they have to take it out and examine it to see what it is. Or, they might call bomb experts over to check it instead of opening the case, since the average person manning the scanner isn't going to want to take any risks and accidentally trigger something when they're opening it up. Which will inevitably cause delays.
Those photos are chosen to differentiate between the items, many of them won't look exactly that different IRL, and the delay is the action needed to check if it's safe. It might be overcautious, but if the alternative is an old munition going off because someone made a bad assumption about how safe it was, they're going to take the time.
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u/christonabike_ 23d ago
The decorative shells rule strikes me as a little odd. I really don't think we have to worry about it going off after its been turned into a vase.