Analysis :: Using Attribute As Second Parameter For FILTER?

For example, I have a Date dimension with attributes like Current Day and Current Month. If I run the following, I get exactly what I expect: a list of the days in the current month.

select
NULL on 0,
[Case - Date - PSPT Entry].[Year - Quarter - Month].[Date] on 1
from [Customer Support]
where
[Case - Date - PSPT Entry].[Current Month].&[True]

When I run the following, I'm getting a list of the days in the current month *plus the first couple days of the next month*. with

set [Days of Interest]
as
filter([Case - Date - PSPT Entry].[Year - Quarter - Month].[Date], [Case - Date - PSPT Entry].[Current Month].&[True])
select
NULL on 0,
[Days of Interest] on 1
from [Customer Support]