Misleading usage of the enum ItemDataRole::ItemTypeRole when using QStandardItemModel::setData in KDGantt

[1molPotato]

Description

The official API documentation for KDGantt suggests using ItemDataRole::ItemTypeRole as the role when setting the ItemType through the QStandardItemModel::setData(). However, when implementing this in practice, setting ItemType with ItemTypeRole does not work as expected and leads to rendering errors in the Gantt chart as below:

Steps to Reproduce

Open the example file <PathToKDChart>\examples\Gantt\legend_example\mainwindow.cpp and modify line 236 to:

model->setData(model->index(row, 1, parent), dialog->type(), KDGantt::ItemTypeRole);

Run the example application and add any new Entry through the dialog.

branch: master(commit e1a206f)

Expected Behavior

Items with Task/Event/Summary type should be rendered correctly in the graphics scene when setting the role with KDGantt::ItemTypeRole.
Or if I misunderstood the documentation and this is a by-design behavior? If so, please provide more detailed explanation why we should assign role with other values (as far as I know, Qt::DisplayRole and Qt::EditRole work well) instead of the more semantics KDGantt::ItemTypeRole.
Actually, I found it necessary to set role as KDGantt::StartTimeRole or KDGantt::EndTimeRole when setting data for start/end time of a task item. So it's weired and apparently inconsistent if the same API is designed to be used in different ways.