In summary, there were 3 hubs and 3 different right side bearings setups from 1952-1978.
Regarding bearing issues.
The most common of all hub complaints is the outer right side bearing being loose in the hub. This is very common on '66→ hubs but not as common '63-'65 and non existent on → '62.
This loose bearing is never a problem in itself. It won't leave you stranded.
Go back to the 2nd pic. The added meat on the drive side flange was incorporated because the earlier hubs would crack thru the thinner flange near where the flange met the tube. The upgrade stopped the cracking but didn't reduce the forces that cracked the hubs.
With this added rigidity, a new problem started showing up.
On a disc brake bike the sprocket is flat or almost flat. Where it connects to the hub there is flange. Under that flange is a bearing. All this is very close to being directly in line with the chain pull. Not so for drum brake bikes. The flange is moved 1-1/2“ off the pull line and the sprockets are cantilevered.
If you stood facing forward, over the rear axle of your bike looking down, you would visualize that as the chain pulls, it also wants to twist the flange (and drum / sprocket) counterclockwise. This twisting of the thin flange would crack it after enough flexing. A rear hub that separates into 2 pieces will put you on the pavement. HD did the right thing by adding the extra meat. Even if it meant (which it did) that this extra meat now transferred that twisting to the hub tube where it would work the outer bearing loose (reasonable tradeoff). A loose bearing beats a loose collarbone every time.
When you jump on the throttle, the hub is being pulled forward by the drive chain in addition to the far right side of the hub getting tweaked farther forward by the counterclockwise flex and it ain't done yet. All this wants to spin the tire on the macadam. Friction here drives the entire bike forward by also driving the hub forward. Except for the weight of the rotating rear wheel assembly, the entire weight of the bike, with you on it, is getting pushed forward thru the fit of 3 little ball bearings in the hub.
Like any other load carrying bearing assembly, the rear axle / hub assembly is alive. It moves around under load (a lot in our case). The assembly moves around from heat also but that's not much of a factor here. Early on in the development of ball bearings, it was discovered that if you affix two or more bearings rigidly to an assembly the bearings will likely fail. If you relaxed the fit so only one bearing in a set was rigidly attached to both the stationary (axle in our case) and the rotating (hub) members and let the others 'float', the life span of the assembly was increased exponentially. You can see this all over our bikes (both hubs, generator, trans door, magneto, crank shaft etc.)
So, the light press fit required to allow the float on the right side did nothing to combat the bearing coming loose. But it did give for a long working assembly with no side effect other than a loose outer bearing.
Then, around 76, the factory abandoned good engineering and tightened up the press fit for the right side bearing set (kissing the float good bye). And just as it was 100 years prior, the assembly as a whole didn't last as long as before. Now the left side single bearing got overloaded because the tight fit doubles on the right bullied it into submission.
Earlier, I said the whole assembly flexes a lot. Transmitted thru the hub, the axle gets the forces too. As the axle flexes, the whole bad scene snowballs.
Look at the 2nd pic again where the naked arrow is. That's where the aluminum back plate butts to the bearing inner race. That race will and does plow rite into the soft back plate when the axle flexes. That's not the best scene either.
Now look at the 62< pic at the same area. Much better. Putting the L58-62 bearing, center spacer and shield into a sweat brazed 66-72 hub gives the best bolt together setup.