I have a PyQt5 QWebEngineView does NOT print the same thing shows in the browser

Question

So I have QWebEngineView app like below

import sys
from PyQt5 import QtWidgets, QtWebEngineWidgets
from PyQt5.QtCore import QUrl, QTimer
from PyQt5.QtGui import QPageLayout, QPageSize
from PyQt5.QtWidgets import QApplication
import argparse

def main():
    parser = argparse.ArgumentParser(description="Just an example", formatter_class=argparse.ArgumentDefaultsHelpFormatter)
    parser.add_argument("--url", help="Type url")
    args = parser.parse_args()
    config = vars(args)
    url = config['url']


    app = QtWidgets.QApplication(sys.argv)
    loader = QtWebEngineWidgets.QWebEngineView()
    loader.setZoomFactor(1)
    layout = QPageLayout()
    layout.setPageSize(QPageSize(QPageSize.A4Extra))
    layout.setOrientation(QPageLayout.Portrait)
    loader.load(QUrl(url))
    loader.page().pdfPrintingFinished.connect(lambda *args: QApplication.exit())

    def emit_pdf(finished):
        QTimer.singleShot(2000, lambda: loader.page().printToPdf("test.pdf", pageLayout=layout))

    loader.loadFinished.connect(emit_pdf)
    sys.exit(app.exec_())

if __name__ == '__main__':
    main()

I run the program like this python3 htmlToPdfnew.py --url https://www.w3schools.com/howto/howto_css_register_form.asp

so IF you load the url https://www.w3schools.com/howto/howto_css_register_form.asp from your browser you will see screen like below

IF you open the output test.pdf, you will see something like below

Compare above screens.

Why they are different ?

How can I get the full screen embedded to pdf like first picture ?

I had a look at online converter https://www.sejda.com/html-to-pdf

That online converter embeds full view to pdf.

So can I achieve the same with above python code ?