Confused about PvP editions

On this page: http://gw.gamewikis.org/wiki/Guild_Wars_PvP_Edition it says:

"150 of the skills for the 6 Core Profession are actually available for each campaign, so if you buy more than one PvP pack then you will get 120 less unique skills and 30 less unique Elite skills than stated."

What does that mean? That you do not get all the skills as stated in the description?

some of the skills listed in each version are CORE skills. core skills are available in each and every campaign. so say, if you have nightfall and buy the factions pvp set, you gain some skills that you already had access to ie those core skills.