Crazy theory.
next week, or maybe in 2, other preview showing the complete new box, with the new units etc..
Pre Order of this box 29th
And the 29th other preview, showing new units of these 2 armies, and a little about the future of this new edition. A kind of celebration.
I think that's what they did with 40k.
It is the only logic that I see so that this month there are 2 more previews, and that the coin has a stormcast logo.