QStorageInfo gets the wrong information for sibling directories to mountpoints

#include <QStorageInfo>
#include <QDebug>
int main()
{
    QStorageInfo sys("/sys");
    QStorageInfo sys1("/sys123");
    
    //  here it can output the right filesystemType :  sysfs
    qDebug() << "/sys fstype:" << sys.fileSystemType();

    //  /sys123 is an existed directory I create, it's filesystemType should be ext4
    //  but it recognize it the same as sysfs
    qDebug() << "/sys123 fstype:" << sys1.fileSystemType();
}