A recent change in the DAX language transformed the behavior of IF statement, so that it should not return BLANK but only TRUE/FALSE if the results should be logical expressions. In that case, the BLANK is transformed in a FALSE condition.
For example, consider that the result of the following expression is FALSE and not BLANK:
IF ( 1 = 1, BLANK(), TRUE )
Checks whether a condition is met, and returns one value if TRUE, and another value if FALSE.
IF ( <LogicalTest>, <ResultIfTrue> [, <ResultIfFalse>] )
Returns a blank.
BLANK ( )