I see if you download the code for Sketch Tool Demo (arcgis-pro-sdk-community-samples/Editing/SketchToolDemo at master · Esri/arcgis-pro-sdk-community-sa... ) they take some additional steps to make sure geometry is in the correct projection.
while (rowCursor.MoveNext())
{
var feature = rowCursor.Current as Feature;
var geomTest = feature.GetShape();
if (geomTest != null)
{
var geomProjected = GeometryEngine.Instance.Project(geometry, geomTest.SpatialReference);
if (GeometryEngine.Instance.Relate(geomProjected, geomTest, "TT*F*****"))
{
cutOIDs.Add(rowCursor.Current.GetObjectID());
if (descriptionIndex != -1)
cutOperation.Modify(rowCursor.Current, descriptionIndex, "ProSample");
}
}
}