QJsonValue::toVariant() result type doesn't match expectation for some numeric input

#include <QCoreApplication>
#include <QString>
#include <QJsonDocument>
#include <QJsonArray>
#include <QJsonValue>
#include <QtDebug>

int main(int argc, char *argv[])
{
    QCoreApplication app(argc, argv);
    // with Qt5 this produces QVariant(double, 2)
    // with Qt6 this produces QVariant(qlonglong, 2)
    qWarning() << QJsonDocument::fromJson(QStringLiteral("[ 2.0 ]").toUtf8()).array().at(0).toVariant();
    return 0;
}