QDateTime comparision is slow even the same timezone is set

The problem was first found here: https://forum.qt.io/topic/159844/comparing-sorting-qvariant-in-qt6

After some investigation I found a minimal reproducer and also an explanation:

const auto d1 = QDateTime::currentDateTime();
const auto d2 = d1.addDays(180);    // make sure it has not the same DST setting
qDebug() << (d1 == d2);

The problem is that 22.11. and 22.11 + 180 days have different DST settings and therefore usesSameOffset() within `bool QDateTime::equals(const QDateTime &other) const` returns false and we've a massive slowdown due to conversion to UTC.
This is due to getStatus() returns 0x8f or 0x4f depending on whether it is inside DST or not.
When I look at the msecs in d->data.msecs I see exactly 180 days difference so the DST flag should not harm here:

((1747853006350-1732301006350)/3600000)/float(24) = 180