Also even though the brochure is from 2012, it seems to already be in line with the then-future new light in its ambiguous description of who the slave is.
That brochure was realeased in 2012. The new light on the faithful and discreet slave was first made public at the annual general meeting in October of 2012. It is very possible that the governing body had come to the new understanding months before revealing it at the AGM, and therefore possible that the brochure was deliberately written in a vague way as to not contradict the new understanding that was about to be revealed.