the old 360BPE with a 57 mm long case was the original, first german modification was 9,3x72R to get more black powder into the cartridge. the 9,3x82R was another update to get 1 gramm BP more.
when smokless powder arive the longer case was obsolete, also the old 57 mm long case could be loaded higher with nitro than the 82 mm case with BP( in theory) but they got all more less nitro for black powder loads.
the 9,3x82R still survive because there were a lot of old combination gun still in use.

the short rifle barrel was a strange idea. see once a drilling with two common shotgun barrels and a rifle barrel underneath. the rifle barrel was just a little bit longer than the stock and you were able to shoot with the drilling hold your hand on the muzzle of the rifle barrel.
people don't thought such a ticking time bomb was worth to have maybe 1 pound less.