Suppose the key comparisons are much more expensive than the array or pointer navigation. Like the article does: it says that it is about theory, and it is look

Suppose the key comparisons are much more expensive than the array or pointer navigation. Like the article does: it says that it is about theory, and it is looking at number of comparisons as the performance measure. The fact that we can search a B-tree node that has, say, 256 children in 8 steps means that the node effectively contains the equivalent of a small balanced binary tree.