Does the /release filtering work with dates?

So I'm trying to fetch all releases for a platform in a specific month like this:

https://www.giantbomb.com/api/releases/?api_key=MYKEY&format=json&filter=expected_release_year:2015&expected_release_month=09&region:1

But I always get back 69968 results which is clearly wrong without filters on dates.

Ideas?