A simple test program produces the opposite results with Qt 6.7.2 and 6.8.0:

#include <QDebug>
#include <QUuid>

int main()
{
    qDebug() << (QUuid::fromString(QLatin1String("{52563609-52e1-4920-8967-4fd28898b75d}")) < QUuid::fromString(QLatin1String("{2b9aa80d-6299-4f35-9c69-0953e7bb9efc}")));
    return 0;
} 

If built with Qt 6.7.2 it prints false. Qt 6.8.0 prints true.

Probably the change is caused by the commit bcfa650ced140daaeb606b69a9b27ffc960da564 which however states that the sorting order is retained.