Yeah it doesn’t seem intuitive, but the bearing inner race is likely the hardened axle and follows the curve. It is a very common problem on cone bearing hubs, and it is the most likely culprit. It is impossible to say for sure without being present and taking it apart to see. I could be wrong. I have not worked as a bike mechanic where I have a ton of direct experience with these specifically. I can fix anything when present or on the road, and have extensive experience with cars, hot rodding, CAT/Case/John Deere heavy equipment, metal fab and machining, not to mention PCB design/fab and FreeCAD/3d printing… Not trying to brag, I’m just adding context. I make mistakes all the time like any human. I have only ever had to replace one bent axle in a rear wheel in my life, but I’ve seen issues mechanics had in passing, and been tasked with tracking down a replacement for them dozens of times. To my best recollection, the only reason for this kind of wobble was a bent axle. Always be skeptical though. “Mod” means nothing to me. I’m just the janitor.