'Flagged' configuration ignores custom field contexts

We are using Greenhopper for some business planning processes and wanted to use the Flagged field, just not the 'Impediment' value.

I created a custom field context for the Flagged field (for all issue types in that project), but Greenhopper never seemed to recognize it and only pulled the default value.

I would have expected greenhopper to have picked up the custom context and have that as the option.