I haven't used it yet, but for $25 or whatever it cost, even if I just use it once I'll be happy. A metal post simply slides through a hole you drill into the floor of the tankbag, disabling the pull cord that is used to remove the Quick-lock tankbag.
I don't want to lose the tankbag, of course. But I'd be more upset losing the contents of the tankbag should it get stolen.
I looked at that, my solution was to put a stainless screw that came with the kit, it appears to be part of the mounting, only problem is you need to pull it out , same as your lock to gas up. I only use it if I am leaving the bike in a area unsupervised and in that case the contents go into my top box.