We have got a configuration that includes a Filter Portlet displayed in a custom tab within the "Project Default Layout" Portlet Page. The filter portlet maps to one or more portlets displayed in the same tab. We notice that when we filter for a value in the Filter Portlet, in one project, and then navigate to another one, the result set and the filter value persists.
Version: 16.0.0.
This is expected behaviour. The result set persists across multiple instances.