The game has been manufactured for all regions.
All distributors have promised to hold the release until Tuesday 28 May 2019 to ensure that the public get any applicable patches to ensure the best day 1 experience. Obviously some distributors have broken the date.... there's not much we at Big Ant can do about that.
If there are any delays in particular countries/regions then I can only think that there have been delivery/customs issues or the like. It would not surprise me if the game became available earlier than is stated, I think that some regions have chosen a "safe" date but they have the agreement to release any time on or after 28 May.
PS: Aussies looking good
Can't believe the idiot in the box gave Smith out....