Pretty sure that by definition, being clinical is how well a player scores goals from the shots they take. Big chances or easy chances, are a bit different. Composure has more impact on the big moments you speak of.
Because Kane is not a far far better player than Lukaku. He might be better, he might be worse, but its definitely not a sure run thing that he is better than Lukaku.
That is the quote. Read it again. I was clearly pointing out that to say that Kane is certainly the better player is not true when there are cases for both to be better at some aspects.