Showcase\Samples in packages - filtering with checkbox

[przelew]

Hello I have propably simple question:
Why in showcase:

http://www.smartclient.com/smartgwtee/showcase/#dmi
and other..

and in downloaded package every sample:
custom-ds
ds-dmi
ds-hibernate
ds-jpa

when I try to filter by selecting checkbox "In Stock" and click "Filter" or "Fetch" I got a result with checkbox "true" and "false" at the same time ??