WTF is this? You trollin?
No im just giving an answer based on scientific evidence thats all. The truth is with your genetic make up you may be able to activate more muscle fibres through a decline bench, which in turn gives you an overall bigger chest, so therefore the lower portion of your pec major is bigger as well. Which may bring you to the assumption that doing decline bench is targetting your lower pec major. Just a guess as your genetics determine this.