I have used that fixing as in your original pic but not on the top.
I did go through a period of bungeeing two locks onto the top of my rack for trips into town - worked fairly well though I had to be careful to strap it well to avoid rattling. And it may be coincidence (and it was an old bike) but after not too long one of the bottom frame mounts for the rack broke off. I wondered if the rattling and stress of two heavy locks moving atop the rack had done this. These days I use mjr's system, slip the locks inside a bag (to cover any oil) then slip that inside a tough ortleib front rolltop pannier on the back. Works far better. Frame fine so far.