Are you trying for in store pick up or delivery?
This is anecdotal, but in my area the in store availability was fluctuating wildly in the week between preorder and release day. I was able to confirm a 256 Natural for release day pick up on Tuesday or Wednesday of last week. I was casually checking the in store availability throughout the workday and it appeared (alongside the other colors and storage configs avail. at different stores) at like 4 in the afternoon.
Idk if the Apple Store allows you to still save your preferred config, but I’d try that and just check when you have downtime. No need to wake up early everyday for a phone.
EDIT: just checked the app and the best way to quickly cycle thru in store availability is to save the config you want instead of adding to your bag. On desktop it’ll also show you alternate configs (higher/lower storage, other colors) at store nearby, if available.