I recall wondering the same thing after I had the bed liner removed and had it sprayed instead, noticed these holes and did a search for bed hooks. I ran into some anchor rings you could use in those holes. I'm not sure if I can link in case the link is not allowed search for.
Bull Ring Bullet...
Gio here from Downey California, had my 2019 Ranger for two months and only done a couple of minor accessory upgrades. Looking to do a whole suspension and tire upgrade, RTT with rack .