Alberto Ferrari explains how different DAX functions treat blank rows differently:
DAX offers two functions to retrieve the list of values of a column: VALUES and DISTINCT. The difference between the two is subtle. To understand it better, we first need to introduce the concept of the blank row. The blank row is a special row added to a table, in case the table is on the one-side of a strong relationship and the relationship is invalid. Let us elaborate on this.
Click through for the detailed explanation, along with plenty of examples.