QSortFilterProxyModel::invalidateFilter() sometimes does not trigger a reevaluation of the model

#include <QCoreApplication>
#include <QSortFilterProxyModel>
#include <QStringListModel>
#include <QTimer>
#include <QDebug>

class CustomProxyModel : public QSortFilterProxyModel
{
    Q_OBJECT

public:
    CustomProxyModel(QObject* parent = nullptr) : QSortFilterProxyModel(parent) {}

    void setFilter(const QString& s)
    {
        if (m_matchString == s)
            return;

        //rowCount(); // Workaround: Calling rowCount() here makes things work
        m_matchString = s;
        invalidateFilter();
    }

    bool filterAcceptsRow(int sourceRow, const QModelIndex& sourceParent) const override
    {
        const auto index = sourceModel()->index(sourceRow, 0, sourceParent);
        if (!index.isValid())
            return false;

        bool accepted = index.data().value<QString>() == m_matchString;
        qDebug() << '\t' << index.data() << "Accepted?" << accepted;
        return accepted;
    }

private:
    QString m_matchString;
};

int main(int argc, char* argv[])
{
    QCoreApplication app(argc, argv);
    QStringListModel model({"1", "2", "3", "4", "5"});

    // ==============================================

    qDebug() << "=== Testing CustomProxyModel ===";
    qDebug() << "Initializing...";
    CustomProxyModel proxyModel;
    proxyModel.setFilter("X"); // Reject all source data at the start
    proxyModel.sort(0, Qt::AscendingOrder); // Trigger an evaluation
    proxyModel.setSourceModel(&model);

    qDebug() << "Invalidating...";
    proxyModel.invalidate();

    qDebug() << "Connnecting signal...";
    QObject::connect(&proxyModel, &QSortFilterProxyModel::rowsInserted, &app, [&] {
        qDebug() << "SIGNAL EMITTED! CustomProxyModel's new rowCount():" << proxyModel.rowCount();
    });

    qDebug() << "Changing filter...";
    proxyModel.setFilter("3");
    // We expect to see a signal emitted here to learn that the proxy model now has 1 row

    // ==============================================
    qDebug() << "";

    qDebug() << "=== Testing QSortFilterProxyModel ===";
    qDebug() << "Initializing...";
    QSortFilterProxyModel qsfpm;
    qsfpm.setFilterRegularExpression("X"); // Reject all source data at the start
    qsfpm.setSourceModel(&model);

    qDebug() << "Invalidating...";
    qsfpm.invalidate();

    qDebug() << "Connnecting signal...";
    QObject::connect(&qsfpm, &QSortFilterProxyModel::rowsInserted, &app, [&] {
        qDebug() << "SIGNAL EMITTED! QSortFilterProxyModel's new rowCount():" << qsfpm.rowCount();
    });

    qDebug() << "Changing filter...";
    qsfpm.setFilterRegularExpression("3");

    // ==============================================
}

#include "main.moc"