Reproduced again, XCode 12.4. And no comments from Apple' tech support at all. Grave silence.

In my case solution was found after month or so discussing with several guys from the tech support. Problem was in the project itself. I set on Maps support in the Signing & Capabilities, but no Routing mode was set, and no Routing area was provided in the AppStore info. page. As soon I removed this entry from the XCode project (as I do not provide route info in release version), error was gone. So my advice is just check for something non-obvious and exclude any features from the project, which are not used.