There is a parallel universe. In this parallel universe, bicycle derailleur systems were originally a primitive, complicated, indexed shifting system. Triples shifted poorly so were dropped. Chainrings required pins and ramps to shift and had to be matched to each other. Outer chainrings required a pin on the outside to catch chain over-shifts. The inner plates of front derailleurs needed to be sculpted and matched to the matched chainrings in order to shift properly or at all. Eventually, 2x drive systems were dropped. Customization of the drive train was limited. Derailleur instruction manuals were pages and pages long and youtube was full of videos on how to make them work. The bike forums were over-run with endless questions regarding the compatibility of various parts and discussions regarding proper set-up and adjustment. “Didn’t you read page 39 of the instructions?” But in time, the bicycle evolved and friction shifting was developed to solve the many shortcomings of indexed drive systems. Issues of compatibility all but disappeared, 3x drive systems became popular and shifted well, pins and ramps and sculpted derailleur cages were eliminated, chain rings became available in almost any tooth count allowing one to customize one’s drive system in endless ways. Instruction “manuals” became a single page. Life became simple and good.