when i have created two posts each has images attached like so:
POST1 - has pictures: 1,2,3 attached
POST2 - has pictures: 4,5,6 attached
when i insert gallery to POST1 with images 1 and 2, then i try to edit gallery i click add to gallery, from media gallery and choose uploaded to this post i see picture 3 and also pictures 4,5,6 (which are attached to another post)
simply i see pictures that are not attached to that post when editting gallery.