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.
return !!(flags & flag);
  }
  /**
   * @private
   */
  _isViewable(flags) {
    return (
      !this._hasFlag(flags, AnnotationFlag.INVISIBLE) &&
      !this._hasFlag(flags, AnnotationFlag.NOVIEW)
    );
  }
  /**
   * @private
   */
  _isPrintable(flags) {