It means that information to the left is always the important part. Right now you have to find the '/', evaluate the components leftwards, return to the '/' and

It means that information to the left is always the important part. Right now you have to find the '/', evaluate the components leftwards, return to the '/' and evaluate components rightwards. Given that finding the '/' is not always trivial (broken screen example in the article) and doing this requires you to think a lot of people won't do it.