The newer Ortliebs intended for off road, the Gravel branded ones, come with two lower retaining hooks so I hope Dan patented the idea! It doesn't always work, some racks need you to hook the bottom on then slide it down at an angle before attaching the top hooks, that wouldn't always work with two pointing in different directions.
Ortliebs promotional stuff shows single retainers pointing either way, so they obviously aren't stipulating which is right. I've always faced mine forwards, I'm using the bottom fitting to stop the pannier sliding forwards, heavy braking will push the hook onto the strut, rather than away from it. I think that possibly takes some rotational force off the top hooks, though seemingly not enough for Ortlieb to be bothered about, so I'm not claiming it's necessary.
With the rear top hook stopping the pannier sliding back, and the bottom hook doing the same forwards, I'm less fussed where I set the top front hook, that leaves me to do so in a way that suits the rack, and by happy coincidence allows me to use my panniers on all three of my racks without adjustment.