Oh, that's much more simple. For short term purposes, ie hills that take less than 5-10 minutes to climb, distance doesn't matter so much. It becomes almost purely a question of total height gained.

Assuming you have adequate gearing, climbing 200' in half a mile at 8% or a mile at 4% in roughly the same amount of time takes comparable effort. This is something that many who have multiple choices to climb the same ridge or hill discover soon enough.

The "only altitude counts" concept breaks down when hills are longer because the time element becomes a factor in its own right.