model.index() returns wrong class

documentation:
https://doc.qt.io/qtforpython-5/PySide2/QtCore/QModelIndex.html#PySide2.QtCore.PySide2.QtCore.QModelIndex.model

says, the return type of model() is a

QAbstractItemModel,

but print(type(model_index.model())) shows

<class 'PySide2.QtGui.QStandardItemModel'>

(run the attached Python script)

problem:

modelIndex.model() returns QStandardItemModel
modelIndex.model() should return QAbstractItemModel

the difference are the signatures:

(1) modelIndex.model().index(row, col ) for QStandardItemModel
(2) modelIndex.model().index(row, col, parentIndex) for QAbstractItemModel

so,
with (1) I never get the proper item in non-trivial trees,
which (2) would allow

I guess that QStandardItemModel.index() has inadvertentlt dropped the 3rd parameter, because just the first two does not make sense.