Just to shed a bit of light onto what likely happened here: As you had never played the game on Battle.net prior to enabling cross-save, you lacked the needed data files on that account. It seems that when people link to, and try to enable cross-save with, a Battle.net account that is not established, the system glitches out. Basically, as there is no save data for cross-save to interact with, no existing files to work with, it creates a new file which overrides everything. Cross-save needs active accounts to work with, but folks are jumping the gun and activating the feature before they have the account data required. And yes, you are stuck with the cooldown period now.