We had this discussion before about the back of a plastic box that ends up within 1.25" of the back wall. The only way I see them justifying this is that the cable entries are in the back of the box so the cable is <1.25" from the edge of the framing.
It would be an interesting question if someone went through a KO in the middle of the box, not the rear edge. You could still shoot a screw into the box but I am not sure there is any language to stop the installation.
Another work around might be to nail up a scrap of 2x lumber, then screw the box to that. A screw shot through the drywall would still hit the box but it would have to be >1.5" off target.
A rocker is usually better than that but a home owner, hanging a picture or something, not so much.
