from an engineering perspective, the hub ring helps locate/centre the wheel when fitting. It does not take any load after that. The load is taken by friction between the mounting faces of the wheel and the hub. If the load was taken by the hub ring, it would need to be an interference fit to avoid fretting.

And yes, its a modern car thing. Some wheels/cars are more sensitive to it than others.
I've used non-hubcentric spacers for years on the 180SX with no problems or vibrations at speeds of over 200kph every track day, using 2 different types of wheels.
But my Aristo road car got a vibration at road speeds from the Volk GT7s I put on it until I picked up a set of plastic hub rings to fit between the Toyota hub and the Volk wheels which had a larger centre bore to suit Nissan fitments.
Since then I always err on the side of caution and get wheels with correct centre bore or at least hub rings to suit - preferably alloy rings, rather than plastic.
I don't think the old Datsun hubs are designed to locate the wheel, front or back, so its not a factor there.