QSettings: can fail to read values written with Qt5

in our effort to move to Qt6 we came across a problem. Fortunately it seems to be only with special types that this fails.

So if you run that code with Qt5

#include <QSettings>
int main()
{     
    QSettings s{QSettings::UserScope, "org", "app"};
    QVariantMap newData{{"1", QVariantList{QByteArray("toto")}}};
    s.setValue("toto", newData);
}  

and then run this code with Qt6:

#include <QSettings>
int main()
{
    QSettings s{QSettings::UserScope, "org", "app"};
    qDebug() << "HAHA" << s.value("toto").toMap().value("1").toList().constFirst();
} 

You would expect that the value printed is a QByteArray.. but no, it is a QVariantList with 1 item that is the QByteArray.

So far I was only able to pro that problem if I write a QVariantMap where values are QVariantList.