This is not working
<criteria system-ref="contentTypes" multiple="true"/>
But this does
<criteria system-ref="contentTypes" multiple="true">
<widget>edition.combobox</widget>
</criteria>

Because, the default widget does return the arry of result as a string.

edition.combobox should be the default as in the configurableformpanel... Is it not a configurableformpanel ????