seems the roller width stopped being thinned at 3/32" then came bushing-less designs,

the inner side plate gets the holes punched and the steel is displaced to form an edge for the roller edges to rotate on
and the pin inside that flange..

As the space is reduced for more speeds, the side plate steel is thinner.. so the flange-bush is thinner as well..

Full Bushing Chains are now labeled as just for IGH & singlespeeds..