Find Roof Soffits Using ElementIntersectsSolidFilter

I'm trying to find all the Roof Soffits that intersect a solid extrusion, but the  ElementIntersectsSolidFilter comes back with no results.

ElementIntersectsSolidFilter filterSolid = new ElementIntersectsSolidFilter(GenerateSolidFromRoom(room));
List<Element> ceilingsAndSoffits = new List<Element>();ceilingsAndSoffits.AddRange(new FilteredElementCollector(doc).OfCategory(BuiltInCategory.OST_RoofSoffit).WherePasses(filterSolid).ToElements());
ceilingsAndSoffits.AddRange(new FilteredElementCollector(doc).OfClass(typeof(Ceiling)).WherePasses(filterSolid).ToElements());

My GenerateSolidFromRoom Method will return a Solid using the GeometryCreationUtilities.CreateExtrusionGeometry Method and my "room" BoundarySegments.

The code will return all Ceiling but never any Roof Soffits.  I can capture all the other Elements in my Room, except Roof Soffits, by using:

ceilingsAndSoffits.AddRange(new FilteredElementCollector(doc).WherePasses(filterSolid).ToElements());

Is there a reason why the Roof Soffit isn't being filtered?