Maybe in the second (68 printing) example Ford choose not to carry both a 6 cylinder and an FE, basically dropping a specific application for the six cylinder. This would reduce inventory, cost and would just mean that six cylinder cars were get a FE starter at possibly a slightly higher price- what ever that was at the time. MPC and service replacement parts was all about what would work and fit while consolidating were possible on parts for used cars.
Just a possibility IMHO
