However, it is clear that Apple wants to move everything to 11. Xcode also says 10.16, but Apple Developer Docs say 11. My suspicion is just that the developers of Xcode and other parts of the OS weren't aware of the switch yet.
Ahh interesting! Yeah, it doesn't surprise me. It's 10.16 now, but I wouldn't be surprised if all of those version numbers will be updated to say 11.0 upon the final production release.