Boardgaming in 2018!

Miniature Market opened up preorders again today for $120 so I canceled my amazon order and placed a preorder with MM since I’m only 45 mins away. I called them to confirm I could pick my preorder up in store and the release date and the employee told me I could and that they were “expecting a release on the 19th”. Hopefully that’s true but I’m still pretty confused by this whole release schedule. If you have the game in stock what are you waiting for at this point? How can they be unsure two days out? How can some stores claim the 19th and others the 24th?