Ortlieb do change them from time to time, I get confused by all the Q numbers and variations! The ones I have, like the ones linked in the OP, don't slide sideways until they've been pulled away from the main body of the hook; they have a lip on both edges. When fitting they click into place, when removing you need to insert something at the end of the insert to pull it away, small flat blade screwdriver ideally, then they just pop out. Don't do it in the long grass, don't ask why I know that's a bad idea.
I don't bother with the inserts, my Ortliebs are used with several racks of different diameter tubing tubing, instead, I've built up the tubing where the hooks sit, doesn't matter with what, though I finish with a couple of wraps of insulation tape, it gets tatty after a couple of years but is easy to replace.