The only angle I saw for an antitrust concern was in delivery where Amazon is already dominant (but not focused on groceries) and Instacart is a serious player who has long partnered with Whole Foods - anytime #1 takes out a significant competitor in a space the FTC could be needed. But there are several more competitors in grocery deliveries including all the legacy companies - Safeway, Kroger, Albertson's, and even Walmart. Basically, this wasn't going to hurt consumers.
