The only difference between a k98 and a k98K is the sights and the length of the barrel. Same barrel, just shorter, which is why a 98 action (the thing that makes it a Mauser) is basically the same. The Enfield denotes the rifling, and lets the buyer know that the rifle has Enfield rifling as opposed to Metford rifling. So it denotes a difference, and since some commercial rifles were based (apparently) on Lee Metford, it's important.