The wheel is OEM from KZ. I just checked it again in case I was dreaming or something, and nope - no taper in the holes. Wheel cannot be reversed either. I'm used to seeing a "bulge" in steel wheels too.
What's even stranger is that it's made in the US by Dexstar. Not a suspect hecho en China item. It's 15x6", "Mini-mod" style, #17-222 which is not on their website.
I spun it around numerous times while gradually tightening the nuts in a criss-cross pattern to try and get the wheel properly centered. Dropped the wheel on the ground and gradually tightened some more. Will drive up our driveway a few hundred feet and check tightness again before heading off down the street and then recheck once more after that.