QGuiApplication removes the main "-platform" parameter

#include "mainwindow.h"
#include <QApplication>
#include <QDebug>
#include <QScreen>

int main(int argc, char *argv[])
{

    for (int i=0; i< argc; i++)
        qDebug() << "main parameter:" << QString::fromLatin1(argv[i]);

    int scaleFactor;
    {
        QGuiApplication a(argc, argv);
        scaleFactor=QGuiApplication::screens()[0]->logicalDotsPerInch() / 96.0f;
    }

    qputenv("Q_SCALE_FACTOR", QByteArray::number(scaleFactor));

    for (int i=0; i< argc; i++)
        qDebug() << "main parameter after QGuiApplication:" << QString::fromLatin1(argv[i]);

    QApplication a(argc, argv);
    return 0;
}

I run the program with the parameter -platform=minimal

The result is:
main parameter: "test123"
main parameter: "-platform"
main parameter: "minimal"
main parameter after QGuiApplication: "test123"

As you can see there is no logs:
"main parameter after QGuiApplication: -platform"
"main parameter after QGuiApplication: minimal"

Why the parameters was removed?

I noticed that QCoreApplicationn doesn't do this.

The first QApplication call removes the "platform=minimal" parameter, so the second QApplication call tries to load the "xcb plugin" instead of "minimal plugin", which ends up with an error "qt.qpa.xcb: could not connect to display"

Is there a way to check the name of the plugin that was loaded the first time QApplication was run ?

Is there a better way to read the pixel density than creating a temporary QApplication object ?