css – iOS and Concentrate on Search Kind on a Webpage: Undesirable Enlargement of the entire web page

I’ve a type subject of the sort “search” on a legitimate* web page:

<search>
    <type motion=https://cse.google.com/cse methodology=get goal=_blank>
      <enter kind=hidden title=cx worth=740064496d7e741b9>
      <enter kind=search title=q title="Suchen in allen Ausgaben von Professional Velo – by way of Google" placeholder="Suchen in allen Ausgaben von Professional Velo – by way of Google">
    </type>
</search>

The code ist a part of my web page: https://provelo.fahrradzukunft.de/

In 3 Browsers on macOS every thing is okay with the behaviour of the search subject.

However on Safari on iOS 18.2 touching the search subject (setting the give attention to the sphere) causes the complete content material of the web page to be enlarged:

What’s the reason behind the enlargement and the way can I forestall it?

*checked on https://validator.w3.org/
The error message “search shouldn’t be allowed inside header” is an error of the validator. In fact it’s allowed.