Is QLSupportsSearchableItems:true required for document-based app quicklook-extension for MacCatalyst?

The WWDC '17 session for core spotlight said QLSupportsSearchableItems is only for "shoebox" apps and explicitly said it's not for document-based apps, but when trying to upload my UIDocumentBrowserViewController-based MacCatalyst app with a quicklook extension (the view-controller-based quicklook preview works great) to App Store connect, it prevents me from uploading without a QLSupportsSearchableItems keys in my quicklook extension's info.plist, and it prevents me from uploading it if the value is false (0).

  1. Is the app store validator correct, and I must have this key and it must be true?
  2. Do I have to implement func preparePreviewOfSearchableItem(identifier, and if so, can I just have it always fail?
  3. If it can't fail, how would I get a sandbox url for the document from a searchable item identifier?

Also, Xcode won't find anything when I search for QLSupportsSearchableItems, which is not so much ironic as it is face-palmy.