Way to communicate contempt for your customers. If you're in the business of selling decorative replicas of cartoon swords, you need to be in on the kayfabe. Nobody is expecting to take one of these to a real swordfight. What they are expecting, however, is to have a cool prop to show their friends, and it's not unreasonable to expect the cool prop to feel like it's not trying to fly across the yard if you swing it around.
If you don't want people to touch the merchandise, the second sign is all you need.
Well it's sorta like an umbrella I guess: better to have one and not need it than need one and not have it. Especially if it rains on the sign or something.
And if someone wanted to check if it is a cheap wall hanger or a replica that could be swung, they might want to do more than just look at it on the wall.
Agreed with your other points but some mall ninjas genuinely believe these could be used haha most people that don't know any better wouldn't know why they couldn't