you have to hit the select al button before submitting.
just because the items are added to the list does not mean they are selected in the target list, you need to select them before submitting.
you could also add the set selected in list behavior to the submit button to select all the items in the target list when the form submits automatically.
The labels cannot be passed on submitting the form, on the action page, you would need to create a recordset to return the items that where selected
my previous example converts the posted array to a comma seperated list. this will be a coma seperated list of the selected ID value.
you could create a recordset as:
SELECT * FROM tableName WHERE idColumn IN (".$_POST['targetList'].")
this will return the records for the selections so you can lookup the labels, of course the method will need to be changed back to POST.