In the retrieve-activity xpath only is the restriction of the objects to retrieve
If the xpath follows any association, like:
[ServiceCalendarv1.Calendar_Consumer/ServiceCalendarv1.Calendar = $Calendar]
than it converts the association to follow the database-link from the first entity, to the association table, and from the association table to the second entity. Have a look at the database by opening pgadmin or the internal database editor (Console → Advanced → Start built in database viewer (a HSQL database)) and look at System.User, System.User_TimeZone and System.TimeZone.
It also allows for restricting per entity like: