Displacement is not a trim level
On a car the fourth dimension is cosmetic often enough that apps treat it as optional. On a motorcycle it is the engine. An 883 Sportster and a 1200 Sportster share a year, a make and a model, and a part that fits one may not fit the other. Any fitment system that files both under "Sportster" will be wrong on a predictable, recurring basis — and the customer finds out after the box arrives.