In file https://github.com/mozilla/pdf.js/files/5249872/product1.pdf, the fifth text widget has a default appearance using font F1 and this one is neither in DR nor in AcroForm but in AP::N::Resources.
if (renderForms) {
      return Promise.resolve(new OperatorList());
    }
    if (!this._hasText) {
      return super.getOperatorList(
        evaluator,
        task,
        renderForms,
        annotationStorage
      );
    }
    return this._getAppearance(evaluator, task, annotationStorage).then(
      content => {
        if (this.appearance && content === null) {
          return super.getOperatorList(
            evaluator,
            task,
            renderForms,
            annotationStorage
          );
        }
        const operatorList = new OperatorList();
        
        
        if (!this.data.defaultAppearance || content === null) {
          return operatorList;