Short rods are an advantage in handling a fish. The short rod gives you more of a leverage advantage (actually, gives the fish LESS leverage.) Never tried a 5 ft. rod, but Lee Wulf used short rods to catch some big fish.
I made a 6.5 2 wt rod that's great for fishing small creeks. I can get 30 ft. of line out, but it's a job. Also, I suspect the way they line-weigh the rods is to kinda guess, close enough is good enough. Mine will throw a 2/3 Teeny line or a 3 WF line just fine.
A 5' rod, if you're standing, is about like a 7' rod if you're sitting as far as distance from the water. So if you can cast a 7' rod from a float tube, you can probably throw a 5' rod standing up.
