I don't know but I'm surprised they take the risk of there not being a tiny perforation.

A can will blow ( can depress the top up and down) if any air gets in. I will buy dented tins, if they are reduced though, but never a blown one.

Mind you years ago all dented tins were put into a bargain bucket type thing with lots of money off. Now they seem to still sell them full price even if dented.