You probably got taught to use a compass also. But you in no way was taught everything you had to know for navigation. Anything you got taught in OW or AOW was just the highlights of more comprehensive courses. The same thing can be said for buoyancy, rescue, equipment specialist.
As Texanguy said, there's different people. I think the "dive only in the same pool you did your OW in" comes from the assumption that the diver's an idiot incapable of getting out of bed without breaking their neck, and then when they do, their next of kin will sue the shop out of business. The flip side is those who assume the diver is capable of kicking against a mild current and will not have a panic attack if they see 80' on their depth gauge. So they get called "lunatic dive masters". Personally I prefer the lunatic ones: I'd rather thumb a dive because it feels too stressful than because it feels like a straightjacket.