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 defaultValue = this.data.fieldValue && this.data.fieldValue !== "Off";
    if (defaultValue === value) {
      return null;
    }
    const dict = evaluator.xref.fetchIfRef(this.ref);
    if (!isDict(dict)) {
      return null;
    }
    const xfa = {
      path: stringToPDFString(dict.get("T") || ""),
      value: value ? this.data.exportValue : "",
    };
    const name = Name.get(value ? this.data.exportValue : "Off");
    dict.set("V", name);
    dict.set("AS", name);
    dict.set("M", `D:${getModificationDate()}`);
    const encrypt = evaluator.xref.encrypt;
    let originalTransform = null;
    if (encrypt) {
      originalTransform = encrypt.createCipherTransform(
        this.ref.num,
        this.ref.gen
      );
    }
    const buffer = [`${this.ref.num} ${this.ref.gen} obj\n`];
    writeDict(dict, buffer, originalTransform);
    buffer.push("\nendobj\n");
    return [{ ref: this.ref, data: buffer.join(""), xfa }];
  }
  async _saveRadioButton(evaluator, task, annotationStorage) {