Bug nella relazione spaziale F ********? (Non sto imprecando)

Mi aspetto che ISpatialFilter.SpatialRelDescription si comporti in modo coerente con IRelationalOperator.Relation . Tuttavia, quando eseguo il codice seguente, ottengo:

    Total features : 44368
    Count1: 9 T********
    Count2: 9 T********
    Count1: 21 F********
    Count2: 44359 F********
    Count1: 1 ******F**
    Count2: 1 ******F**

È un bug nella F********relazione?

private void TestSpatialFilter()
{
    IMxDocument mxdoc = ((IApplication)m_application).Document as IMxDocument;
    IFeatureLayer fLayer = mxdoc.FocusMap.get_Layer(0) as IFeatureLayer;
    IEnvelope env = ((IActiveView)mxdoc.FocusMap).Extent;
    env.Expand(0.5, 0.5, true);
    env.Project(((IGeoDataset)fLayer.FeatureClass).SpatialReference);
    Debug.Print("Total features : {0}", fLayer.FeatureClass.FeatureCount(null));
    IFeatureClass fc = fLayer.FeatureClass;
    string[] rels = { "T********", "F********", "******F**" };
    foreach (string rel in rels)
    {
        Debug.Print("Count1: {0} {1}", Count1(fc, env, rel), rel);
        Debug.Print("Count2: {0} {1}", Count2(fc, env, rel), rel);
    }
}

public static int Count1(IFeatureClass fc, IGeometry geom,  string relDescription)
{
    ISpatialFilter sf = new SpatialFilterClass();
    sf.SpatialRel = esriSpatialRelEnum.esriSpatialRelRelation;
    sf.SpatialRelDescription = relDescription;
    sf.Geometry = geom;
    int i = fc.FeatureCount(sf);
    Marshal.FinalReleaseComObject(sf);
    return i;
}
public static int Count2(IFeatureClass fc, IGeometry geom, string relDescription)
{
    int i = 0;
    string relation = String.Format("RELATE(G1,G2,'{0}')", relDescription);
    IRelationalOperator relOp = geom as IRelationalOperator;

    IFeatureCursor fCur = fc.Search(null, false);
    IFeature feat;
    while ((feat = fCur.NextFeature()) != null)
    {
        if(relOp.Relation(feat.Shape,relation))
            i++;
    }
    Marshal.FinalReleaseComObject(fCur);
    return i;
}

Sembra strano. Forse è stato testato solo con poche operazioni specifiche, ad esempio: Intersects, Disjoint, ecc.? Cosa fa FF*FF****(inverso di T********) per te? Mi sembra di ricordare che Inside non abbia funzionato alcune versioni, quindi non mi sorprende.