QVariant::toString() has a different output between 5/6 on floating point (double) numbers

#include <QVariant>
#include <QDebug>

int main()
{
    double d = 200000;
    QVariant v = d;
    qDebug() << v;
    qDebug() << v.toString();
    qDebug() << QString::number(d, 'e');
    qDebug() << QString::number(d, 'f');
    qDebug() << QString::number(d, 'g');
    qDebug() << QString::number(d, 'g', 128);
    qDebug() << QString::number(d, 'g', -128);
}

QVariant(double, 200000)
"200000"
"2.000000e+05"
"200000.000000"
"200000"
"200000"
"200000"

QVariant(double, 200000)
"2e+05"
"2.000000e+05"
"200000.000000"
"200000"
"200000"
"2e+05"