maybe its because we create less chances so the big missed chances are more costly. in other words, lukaku might have less big chances missed than kane last season, but his missed chances could have made up a greater percentage of the team overall's big chances.
eg. Team A creates 50 big chances, scores 30, misses 20, 11 of those are lukaku misses. Team B creates 100 big chances, scores 60, misses 40, 18 of those being kane's. Here Kane has missed a lower percentage of his team's big chances than Lukaku.
Anyway yeah I would be interested to know how many of Lukaku and Kane's big chances missed were in defeats or draws. It feels as though Kane is more clinical and wouldn't miss many 1 v 1s against keepers.