Nowhere does it ever specify that the publication is shounen in any Japanese documentation, it's described as 中・高校生男女 which means 'in-between, targeted towards highschool boys and girls' which means that no demographic should be listed to it, as none of the currently used demographics fit for both. And in the majority of series and subscriber base, it is clear that the magazine is much more heavily focused towards girls, yet not entirely, hence why shoujo wouldn't work either.

The shounen tag should be removed from all published series in the magazine.

Actually that means both tags, shoujo and shounen, should be added to each series if anything.

Just noticed this is posted in the Kuroshitsuji locked genre section if tried to edit.

Reason: It's shounen because it's published in GFantasy, so stop changing it

GFantasy isn't specified as a shounen publication, please give me a valid source that states it as such, nowhere does it show that it is solely that.