I'm a little puzzled as to the use of the following parameter on the ITermSearchService.Search(...) method:

public interface ITermSearchService
{
    IList<ISearchResult> Search(string text,
                                ILanguage source,
                                ILanguage destination,
                                int maxResultsCount,
                                SearchMode mode,
                                bool targetRequired);
}

While searching from the Termbase Search panel or by entering a segment the value false is passed as an argument.

When will this parameter be set to true and what does it represent?