Why do I need experience on winter graded ground?

In winter time the boundary between hill walking and mountaineering is very blurred. For example very icy underfoot conditions coupled with snow build-up can turn what was an innocuous slope into something far more technical and challenging. In such a situation the Winter Mountain Leader has to be able to move about the ground in a skilful, relaxed and efficient manner so that they can devote their full attention to managing their team. Hence there is a requirement for a Winter Mountain Leader to be able to move about on this type of mountaineering terrain. It can be difficult to quantify whether candidates have this experience, hence having a requirement to have completed 10 Grade I climbs or equivalent mountaineering routes is a shorthand way of ensuring that a Winter Mountain Leader candidate has definitely had experience of moving on steep terrain.