Turning JavaScript on in acceptNavigationRequest doesn't always work

#include <QApplication>
#include <QWebEngineView>
#include <QWebEnginePage>
#include <QWebEngineSettings>
#include <QUrl>
#include <QTimer>
#include <QDebug>

class WebPage : public QWebEnginePage
{
    bool acceptNavigationRequest(const QUrl &url, NavigationType type, bool isMainFrame);
};

bool WebPage::acceptNavigationRequest(const QUrl &url, NavigationType type, bool isMainFrame)
{
    qDebug() << url;
    if (isMainFrame && url.toString().contains("travis-ci")) {
        settings()->setAttribute(QWebEngineSettings::JavascriptEnabled, true);
    }
    return true;
}

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QWebEngineView view{};
    WebPage page{};
    view.setPage(&page);
    QWebEngineSettings::globalSettings()->setAttribute(QWebEngineSettings::JavascriptEnabled, false);

    view.load(QUrl("https://www.example.com/"));
    view.show();

    QTimer::singleShot(2000, [&](){ view.load(QUrl("https://www.travis-ci.com/")); });
    QTimer::singleShot(4000, [&](){ view.reload(); });

    return app.exec();
}