you can surely use Firebug's "Net" tab to determine if accordion makes Ajax (XHR) server request to update dataGrid area.
In this case, it depends on switchType setup for accordion and particular accordionItem.
You can setup switchType either client or ajax or server.
And you can find more according to accordion in documentation .
some additional notes not to the loading by ajax but about code itself.
1) http://docs.jboss.org/richfaces/latest_4_0_X/vdldoc/a4j/region.html region has no such attribute. And not sure what you want to achieve with that there.
2) <a4j:outputPanel> rendered as span by default. And inside you using table(grid) and div(panel). That's not good.
Post should be moved to RichFaces space. That space for RF design discussions.