The BG3 website says :

"All of the Digital Deluxe Edition DLC content is also included with the Collector’s Edition, which gives you 72 hours Early Access [...]"

The CU#20 : "petite précision : les sauvegardes de l'accès anticipé ne seront pas transférables dans le jeu ; en revanche, celles qui seront créées dans les 72 heures de jeu anticipé juste avant le lancement officiel, si" which means : "little precision : savegames from the EA won't be transfered in the game ; on the other hand, those created in the 72 hours of anticiped game before the official release will."

The CU#18 shows a board indicating '"Early access to act I" for the Deluxe and Collector editions.

It never refers to a date. They sold editions with early access of 72h so they must deliver it to customers who purchased these editions otherwise it's illegal. It might seems trivial (yeah we speek about 3 days of anticiped game) but this is just a legal question. This anticiped access is sold. So it is due. The modification of the official release date does not change the content of the editions already sold.

Buying something is the result of a sale contract : buyer must pay according to the rules of the contract and the seller must deliver what is in the contract. If not, the contract is broken and customers must be compensated.