I think Table does not use filterType property in sorting. Example from sap.ui.table.Table code:
this._oSorter = new sap.ui.model.Sorter(this.getSortProperty(), this.getSortOrder() === sap.ui.table.SortOrder.Descending);
aSorters.push(this._oSorter);
....
// sort the binding
oTable.getBinding("rows").sort(aSorters);
So I think your best bet is to do as in Angel Puertas blog.
Regards,
Kimmo