I think there is some overstating of the "merger v acquisition" terminology in here. Most all acquisitions are technically mergers, but in most all cases everyone knows which company is buyer and which is seller, as is very obvious in this case. For legal / tax reasons, a temporary legal entity is created to make the purchase, then is merged into the parent entity. Its a purely legal maneuver, not generally considered a marketing thing, but I get the point. The DFH branding is one of the most valuable assets Boston Beer is acquiring. All their press releases will emphasize that entity will maintain complete independence and control over its products (it won't).
In the case of ABInBev buying Goose Island, that deal caused major concern in the beer geek community, mostly because it was on the front end of these acquisitions (or "sell-outs" depending on your viewpoint.) But from the very beginning, if you actually listened to the InBev and Goose Island people, there was really no need for concern. InBev wanted Goose Island's 312 brand, an established wheat ale they wanted to compete with Miller/Coors Blue Moon. InBev was able to brew that beer and immediately distribute it nationwide. The beer geeks don't care about 312, they cared about Goose Island's funky sour beers and their big black barrel aged stouts. ABInbev was never going to touch those brands, and they remain the same to this day. There are multiple reasons for this, but the most important is that those beers and their markets don't lend themselves to large scale distribution. I'm sure they are profitable, but not on a macro level, if that makes sense, for a number of reasons.