Chromium is a complex sub-system with a huge set of internal flags, toggles and options. It could be nice to provide an API to that one can update these settings.
It turned out QWebEngine implicitly support zoom via gestures on MacBook touchpad. This zoom factor does not reported into the page()->zoomFactor API. Neither can we change disable the feature. Googling shows it is possible to disable such behaviour via chrome://flags. Could be nice to be able to set those flags for embedded browser.