We can agree that the standard set up , allowing gear oil to reach the friction plates is a design error .
IMO , it is better engineering to correct that mistake by making better parts , than to add another part to hide the symtoms .
( like wearing a pamper if you are ...)
It is not the bearing ball that prevents the oil from migrating , but the end piece .
The bearing ball only helps to stop the rod from grinding away against the inside of the mainshaft .
I probably assume too quickly that people who's hobby it is to own and ride old cars , bikes , boats ... also have the skill and tools to maintain them .
Apparently this is not the case ( hence the 5000 ..) .
Many have to rely on services provided by others , and parts they can readily buy .
For them ,your CR seal is a great solution .