xforms-select event doesn't happen for the default xf:case when the form is loaded.
When the form is loaded, the instance('inst-x')/case-a node should be set to the value 'Case A selected' by the xf:setvalue in the xforms-select handler. It's only when the appropriate trigger is clicked that the xforms-select handler gets executed.
Tested with formsPlayer 1.6.1028.0