QtQuick software renderer does not work with fractional scaling factors

import QtQuick 2.12
import QtQuick.Window 2.12
import QtQuick.Controls 2.12 as C
import QtQuick.Layouts 1.12

Window {
    id: root
    visible: true
    width: 600
    height: 400
    title: qsTr("Hello World")

    ColumnLayout {
        anchors.centerIn: parent
        C.Label {
            text: "devicePixelRatio " + Screen.devicePixelRatio
        }
        Grid {
            flow: Grid.LeftToRight
            spacing: 1
            columns: 10
            Repeater {
                model: 100
                Rectangle {
                    height: 30
                    width: 30
                    color: "blue"
                }
            }
        }
    }
}

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QFont>

int main(int argc, char *argv[])
{
  QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);

#if QT_VERSION >= QT_VERSION_CHECK(5, 14, 0)
  QGuiApplication::setHighDpiScaleFactorRoundingPolicy(Qt::HighDpiScaleFactorRoundingPolicy::PassThrough);
#endif
  QGuiApplication app(argc, argv);

  QFont f("Segoe UI");
  f.setPixelSize(12);
  app.setFont(f);

  QQmlApplicationEngine engine;
  const QUrl url(QStringLiteral("qrc:/main.qml"));
  QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
                   &app, [url](QObject *obj, const QUrl &objUrl) {
    if (!obj && url == objUrl)
      QCoreApplication::exit(-1);
  }, Qt::QueuedConnection);
  engine.load(url);

  return app.exec();
}