The only time that a steep approach is necessary at BGBW is when there is a strong wind up the valley. In that situation the effective approach angle into wind is considerably less than it would be with zero wind.
Many years ago I recall watching an SAS DC8-63 approaching down the glacier at BGBW, landing on the runway which also slopes down towards the fjord!
An exciting landing, needless to say, but they did get it stopped.