Say typical Bendix style brakes, like F1. Short shoe goes to front, long shoe to rear. So if the short front shoe was replaced with another long shoe what would it cause to happen? Too much self energization or just more?
Maybe less, originally the primary or front shoe was a “grabbier” friction material. Now I think they are all the same, I doubt you would ever notice a difference either way.
I recently had some original Lincoln shoes relined by a big brake shop in Minneapolis. They came back the same length, with the same material on each. It will be a few months til I road test them, but I'm guessing the place does it like that for a reason. Maybe the different lengths never made much difference in performance?
It is normally short shoe in front long shoe in rear but there are manufactures that use shoes with two different friction coefficient that are the same length. Those linings are usually two different colors and marked front and rear. They were the "cheap" shoes in the 70's That didn't last a lot of miles or stop that great if you were making stops from 80 mph but for those cars that folks just drove around town they never brought noise or pulling complaints. There also used to be some shoes that had a groove in the middle of the front lining rather than a shorter lining. That again in the 70's when I was doing a crap load of brake jobs every week. As long as your linings are matched side to side you should be ok. short lining on one side and long lining on the other will cause the brakes to pull though.
If you had a set of brakes with specific primary and secondary shoes and you didn't install them in the proper orientation, you might be more likely to experience some strange braking on a vehicle with drums on all four corners. On something with front disks and only rear drums I suspect you might not even notice a difference.