Accessing WindowFlags through postEvent causes Application to not exit

class QEventExecutor : public QEvent
{    
using callback_t = std::function<void()>;
  private:    
callback_t m_func;
  public:
    QEventExecutor(callback_t &&func) : QEvent(QEvent::None), m_func(std::move(func)) {}
    ~QEventExecutor() override
    {
        m_func();
    }
};

// Somewhere else in a different thread
QApplication::postEvent(/*receiver*/, new QEventExecutor([] {/*...*/}));

#include <QApplication>
#include <QMainWindow>
#include <functional>
#include <future>
#include <thread>

class QEventExecutor : public QEvent
{
    using callback_t = std::function<void()>;

  private:
    callback_t m_func;

  public:
    QEventExecutor(callback_t &&func) : QEvent(QEvent::None), m_func(std::move(func)) {}
    ~QEventExecutor() override
    {
        m_func();
    }
};

int main(int argc, char **argv)
{
    auto QApp = QApplication(argc, argv);
    auto *main = new QMainWindow();

    main->setWindowTitle("Bug Report");
    main->setFixedSize(500, 600);

    // auto fut_ptr = std::make_shared<std::future<void>>();
    // *fut_ptr = std::async(std::launch::async, [fut_ptr, &main] {
    //     std::this_thread::sleep_for(std::chrono::seconds(2));
    //     QApplication::postEvent(main, new event_callback([&main] {
    //                                 main->setWindowTitle("Works, application exits!");
    //                                 main->close();
    //                             }));
    // });

    auto fut_ptr = std::make_shared<std::future<void>>();
    *fut_ptr = std::async(std::launch::async, [fut_ptr, &main] {
        std::this_thread::sleep_for(std::chrono::seconds(2));
        QApplication::postEvent(main, new QEventExecutor([&main] {
                                    //? Doesn't work, window closes, application doesn't exit
                                    main->setWindowFlag(Qt::FramelessWindowHint, true);
                                    main->close();
                                }));
    });

    main->show();
    QApplication::exec();
}