Okay, I have reviewed this and it appears that GEMS unfortunately does not handle (and has not ever)the above case. Significant headers can be used to put a header on only the democratic ballot, but they cannot be used to force a democratic ballot when there are no democratic races.
For 1.11 at least, the best I can offer is a work around. Create a race with no candidates as a psudo significant header. This race will differentiate the ballots for GEMS. This race can be the "Official Ballot" header, or something more inert like a seperator with actual significant headers in turn attached to it.
What exactly is the difference between the absentee and polling header in Gwinnett anyway? If it is something simple like displaying "Official" instead of "Absentee", we might be able to handle this with an @vgroup macro in the same spirit as the @precinct macro, without a major GEMS upgrade.