They at least control the angle at which the load pulls, and have some notion of what the anchor points will experience in transit.The tie down hooks don't go into the bumper, they go into the frame. What do you think would happen if it was attached to the bumper in heavy seas in the Pacific?
I suspect Mazda wants to be clear that they don't endorse customers using those points, so its proceed at your own risk.
One thing I've noticed with the 2nd Generation, compared to the first, is that the bumper around the eyelet cover, is painted with Mazda's exotic and fragile paint. In the 1st gen, it was black plastic.
So its much easier to do expensive damage (scratching or worse to Soul Red Crystal painted surfaces) on the 2nd Gen.
I lost the driver's side rear eyelet cover on mine