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 )

I wrote a longer explanation of that, thanks to Jeffrey Wang who provided the details of the implementation. Also a big thanks to Darren Gosbell, who raised the initial question.

Originally appeared on: http://sqlblog.com/blogs/marco_russo/archive/2016/09/14/blank-and-boolean-functions-like-if-in-dax.aspx