From what I can tell the use case for .nosync there is to store a large dataset in a SQLite store in such a way that individual transactions are replicated to iCloud but the entire SQLite store itself is not transferred each time something changes.

The documentation seems to imply that .nosync will prevent the whole store from being uploaded, but (1) that does not seem consistent with what others are reporting, and (2) I cannot find any other supporting information on .nosync in either Apple documentation or dev forums - that doc and this thread are literally the only places I've seen it referenced.

The other underlying issue is whether Apple would be cool with storing persistent application data in Documents provided that it is not synced to iCloud. The use case that Marco and others have described does not really match what's described in that document.

edit: Marcos -> Marco