There was a service bulletin on that very subject back in "the day". The hub is cast into the flywheel, but they were coming loose. The hub design was changed as a result. It is still cast into the flywheel, but is much more robust. I'd have to dig up the info, but to the best of my recall, the redesigned flywheel had a "Q" stamped near the rope notch. People were rejecting the redesigned flywheel because hairline cracks were appearing between the puller holes. The bulletin explained that those cracks were only on the surface and not a problem nor a cause for replacement.
P.S. I would never tell anybody to run a damaged flywheel or crankshaft. That thing can kill or maim if it gets loose. I saw a guy that it happened to. Not a pretty sight.