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.
const strokeColor = this.color
          ? Array.from(this.color).map(c => c / 255)
          : [0, 0, 0];
        this._setDefaultAppearance({
          xref: parameters.xref,
          extra: "[] 0 d 1 w",
          strokeColor,
          pointsCallback: (buffer, points) => {
            const dy = (points[0].y - points[2].y) / 6;
            let shift = dy;
            let x = points[2].x;
            const y = points[2].y;
            const xEnd = points[3].x;
            buffer.push(`${x} ${y + shift} m`);
            do {
              x += 2;
              shift = shift === 0 ? dy : 0;
              buffer.push(`${x} ${y + shift} l`);
            } while (x < xEnd);
            buffer.push("S");
            return [points[2].x, xEnd, y - 2 * dy, y + 2 * dy];
          },
        });
      }
    } else {
      this.data.hasPopup = false;
    }
  }
}
class StrikeOutAnnotation extends MarkupAnnotation {