Why is WvW part of PvE map completion?
because they want you to enjoy all parts of guildwars 2
WvW is a part of the actual “world” of guild wars. It’s part of the universe as a place of limbo-esq that has an effect on Tyria. For example the bonuses earned in WvW for crafting, gathering, xp, karma, ect are all granted in the PvE zones as well. They aren’t as separate as you think, but rather WvW is more like an extension of PvE.
(edited by Tadzio.2173)
Why do you assume world map completion is PvE? I think is quite obvious from your very question that it is not.