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 (!dict.has("QuadPoints")) {
    return null;
  }
  
  
  const quadPoints = dict.getArray("QuadPoints");
  if (
    !Array.isArray(quadPoints) ||
    quadPoints.length === 0 ||
    quadPoints.length % 8 > 0
  ) {
    return null;
  }
  const quadPointsLists = [];
  for (let i = 0, ii = quadPoints.length / 8; i < ii; i++) {
    
    
    
    quadPointsLists.push([]);
    for (let j = i * 8, jj = i * 8 + 8; j < jj; j += 2) {
      const x = quadPoints[j];
      const y = quadPoints[j + 1];
      
      
      
      
      if (
        rect !== null &&
        (x < rect[0] || x > rect[2] || y < rect[1] || y > rect[3])