MN restaurant beer list strangeness

Pretty sure he's referring to this- http://www.ehow.com/how_6128867_open-beer-can-bottom.html

 

It's a habit/peeve of older collectors (and mainly a habitual relic of a time when steel cans with thinner / more porous linings would rust-through and spring a leak, thus the eventual use of the collector's term: "leakers" -- http://www.beercanworld.com/beercans_faqs.htm#9 )