I didn't receive a seperate code for Shadowbringers, only the one to register Endwalker pre-order which also contained the pre-order bonus items. On mogstation it also says that I didn't buy Shadowbringers yet. The confirmation email does say
You will be notified by email before we debit your account, which will normally occur 1-4 weeks before the release date of the item
since I paid with paypal and it may take a while till my account gets charged for the purchase.