The lenght of rod is in international rules based on the distinct difference between single and double handed rods. my grandfather used salmon rods over 12 ft and built with double handed cork handle. He refered in the dirary that the classic sea trout rod (talking cane here) was 10ft and "beautifially light" to use!.
So loch style fishing had the biggest at the time single handed casting rods that materials (at the time allowed for) break you wrist tying to cast a 13ft rod single handed made of cane! or for that matter fibre glass.
Not to mention trying to present a dry fly with a salmon rod on the test would raise some eye brows!