According to the official IMPS specifications for a Boston Butt, if you take a whole shoulder and cut off the picnic.... everything left above the picnic is a Boston Butt.....
But most people don't find them that way in their stores. Another horizontal cut has been made that removes the meat above what you are used to seeing. What remains though, is still a Boston Butt. So there is a lot of meat you aren't used to seeing on your Boston Butt that is still officially part of the Boston Butt.
Iron Pig BBQ - www.IronPigBBQ.com - "Reverse Sear" info on website