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 dict = new Dict();
    dict.set("BaseFont", Name.get("ZapfDingbats"));
    dict.set("Type", Name.get("FallbackType"));
    dict.set("Subtype", Name.get("FallbackType"));
    dict.set("Encoding", Name.get("ZapfDingbatsEncoding"));
    return shadow(this, "fallbackFontDict", dict);
  }
}
class ChoiceWidgetAnnotation extends WidgetAnnotation {
  constructor(params) {
    super(params);
    
    
    
    
    
    
    
    
    
    this.data.options = [];
    const options = getInheritableProperty({ dict: params.dict, key: "Opt" });