I have the same problem with Xcode 13.2.1: I have many .scn files and none seems to work. However, at compilation time I get the warning Could not find b undle inside /Library/Developer/CommandLineTools scntool the bundle indeed seems to be missing. It was working with Xcode 11, about one and a half year ago

As far as I understand it, you create a "stubby" new release, you edit the age restriction data, and you leave it as it is. When you really have to submit a new release, you can take it from there with a build upload and all that is needed. A bit clunky. Why not simply allow to edit the form for the current release? You can change other data after all.