That was my first reaction, until i remembered that i've seen a globe before, and my general perception of the shapes of countries is informed by a globe and not just the mercator projection.

This map might bill itself as "the most accurate", but it's still making some crazy distortions. Mercator might get some sizes wrong, but it gets the shapes mostly right.

That is a distortion, I think. Look at the longitude and latitude lines in the sea.

It looks as if this map generally is designed to localize the inevitable shape distortions to areas where there isn't "interesting" detail and therefore those distortions aren't as obvious. But because of the way Brazil sticks out, it ended up getting stretched a fair bit.