I think I understand what is causing your confusion. You are mixing up a driver's license with an OW certificate. When a new driver gets a learner's permit he is allowed to drive under certain conditions with a licensed driver. Once you get your license you are free to drive solo on any public road.Yes. It's like when you first get a driver's license. There's a period of time when you have a training license, and aren't supposed to drive without an experienced driving in the car with you.
I don't think anybody who has only done OW is qualified to dive without a DM. Not me, and not anybody else either. And SB members are welcome to tell me I'm incompetent, or dumb, or didn't pay attention in class, etc. But I disagree. Nobody fresh out of driver's ed is qualified to drive with only another fresh driver, and nobody fresh out of OW is qualified to dive only with another new OW graduate buddy.
An open water certificate allows you to dive in conditions similar to your training, no matter who you dive with. My late wife and I got certified together and made more than 600 dives together, all without a DM. Every diver I know gets certified and goes out diving with anyone who will dive with them. Perhaps you should join a local dive club and see how much diving is done without a DM.