I have to admit that I am not impressed with the title. It is wrong. According to your article, the column order in a composite index is not important.

From the article you state, "Let's now reverse the order of the WHERE clause in the select statement. If you now run the select statement shown below you will still see the same execution plan as shown in Fig 1."

This article states that composite indexes work better when all columns in the composite index have an explicit value in the WHERE-clause. The composite index is less efficient when one or more of the columns in the index are omitted. Column order is irrelevant. Column presence is.