QHeaderView is very slow (unless it is used with only few data)

#include <QTableView>
#include <QStandardItemModel>
#include <QHeaderView>
#include <QApplication>
#include <QElapsedTimer>
#include <QDebug>

const int rowcount = 50000; // Ok it is many, but a DB can easily hold 1.000.000 rows 
                            // There are also gains for lesser rows - on slow machines (e.g boards or phones) this would also be very relevant

int main(int argc, char *argv[])
{
  QApplication app(argc, argv);
  QStandardItemModel m;
  m.setRowCount(rowcount);
  m.setColumnCount(19);
  QString tmp;
  for (int u=0;u<rowcount;++u)
  {
    tmp.setNum(u);
    m.setData(m.index(u,0),u);
  }
  QTableView v;
  v.setModel(&m);
  v.setGeometry(10,10,400,400);
  v.show();
  
  QHeaderView *h = v.verticalHeader(); 
  QElapsedTimer t;
  qDebug() << "Staring Timer.\n";  
  t.start();
  h->moveSection(0,rowcount-2);
  qint64 endtimer = t.elapsed();
  qDebug() << "Moving index time: " << endtimer << "\n";
  t.start();
  m.setRowCount(10);
  endtimer = t.elapsed();
  qDebug() << "Removing a lot of rows: " << endtimer << "\n";

  qDebug() << "Notice we are just doing ONE operation";
  qDebug() << "swapSction,resizeSection,hideSection are also a bit slow  ";
  qDebug() << "The above just makes ONE call to ONE operation. When I want to sort with swapSection or hide many it is horrible!";
  
  app.exec();
}