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 (Array.isArray(formValue)) {
      return formValue
        .filter(item => isString(item))
        .map(item => stringToPDFString(item));
    } else if (isName(formValue)) {
      return stringToPDFString(formValue.name);
    } else if (isString(formValue)) {
      return stringToPDFString(formValue);
    }
    return null;
  }
  /**
   * Check if a provided field flag is set.
   *
   * @public
   * @memberof WidgetAnnotation
   * @param {number} flag - Hexadecimal representation for an annotation
   *                        field characteristic
   * @returns {boolean}
   * @see {@link shared/util.js}
   */
  hasFieldFlag(flag) {
    return !!(this.data.fieldFlags & flag);
  }
  getOperatorList(evaluator, task, renderForms, annotationStorage) {