The first announcement involves which products retailer can sell during prerelease events. For the Dominaria United prerelease, WotC had opened up sales of Collectors Booster as part of their early sales offerings (see "More Deets for 'Dominaria United' Release"). For Brothers' War, all of the products in the line (see "The Brothers' War' Product Line") are fair game for retailers to sell to their patrons during the prerelease event window.
The second announcement revolves around the timing of digital set release and in-store prereleases. Previously, WotC announced that their Magic: The Gathering - Streets of New Capenna prereleases would occur at FLGS before the digital release of the product as a test run (see "Prioritizes FLGS 'Magic: The Gathering' Prereleases Over Digital Release"). For Brothers' War, they have decided to once again run tabletop preleases before the digital release, and do so again for the next two Standard sets (Phyrexia: All Will Be One and March of the Machine).