Shell feature - can't "Edit References" after creation - Creo 10

In Creo 10.0, items in the "Remove surfaces" field in the shell feature dialogue box cannot be replaced later using the "Edit References" command; they must be removed and reselected from within the Shell feature tool.  The "Edit References" option is greyed out when the shell feature is selected. This is unusual behavior among Creo features, in which lost surfaces can be replaced by newer surfaces by using "Edit References" without entering the feature tool after the feature has been created.  This is useful when you prefer not to redefine and reselect manually, e.g. drafted wall become straight.  I don't recall that this was the case in earlier versions.   Is it a bug?