Im surprised how many people don't see through the extremely thinly veiled marketing effort. This isn't a "lets celebrate world peace" effort by BK, it's a way to make them look like good corporate citizens, while also marketing their food over McD. Even the name.. McWhopper - its mostly whopper. The branding on McD is falling off the bag to the left, while WHOPPER is prominent. The "buildup" of the burger features mostly whopper ingredients, and a blatant size difference between the top half of the Big Mac, and the entirety of the whopper (minus top bun).

Here's a prime example: http://prntscr.com/8994ka Notice the red part takes up less than half the screen, its falling off to the left. BK has been for years pointing out the difference in size of a whopper patty and a big mac. Here they found a great way to juxtapose the two, while making social media denizens feel all warm and fuzzy. They know McD wouldn't do this - another score!

Marketing!