Ya those bearing retainers really bite.
I looked in one of the old Honda factory manuals I have and they tell you to drill out the factory "staking" or upset - ie, the factory peening of the retainer. Not having the recommended metric drill bit, I used a 3/16 drill and the retainer threaded out easily afterwards.
When I put the new wheel bearings in, I "restaked" the retainer. The bike I was rebuilding had over 27,000 miles on it with the factory bearings and I doubt whether the bike will ever see that many again, so I'm pretty safe on another rebuild...
Of course, I read the manual after I abused the rear hub from one of my 350's, ending up with a multipiece retainer similar to the one in the photos - thankfully, had a few spares around.
Once I grokked to the staking thing, I started looking around at other ancient stuff I have and some of my older bike manuals and it seems like it was a pretty common method awhile back. Honda for some reason kept doing it with their bikes well after everyone else figured out alternate and modern methods to stop bits from loosening.
Its all good fun.
Pat