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.
/**
   * Set the dash array.
   *
   * @public
   * @memberof AnnotationBorderStyle
   * @param {Array} dashArray - The dash array with at least one element
   */
  setDashArray(dashArray) {
    
    
    
    if (Array.isArray(dashArray) && dashArray.length > 0) {
      
      
      let isValid = true;
      let allZeros = true;
      for (const element of dashArray) {
        const validNumber = +element >= 0;
        if (!validNumber) {
          isValid = false;
          break;
        } else if (element > 0) {
          allZeros = false;
        }
      }
      if (isValid && !allZeros) {
        this.dashArray = dashArray;
      } else {
        this.width = 0; 
      }