Specifically, the references to 60fps, mobile, and 8.8 million lines are all jokes. I hate to explain jokes. But I see a lot of people in the comments trying to read serious deep meaning into these that is just not there.
They used the same speed, mobile and "too many lines of code" comment, IIRC.
Also, knowing that Google really pushes and wants the Shadow DOM (see recent hoopla with W3C about them shipping their own version ahead of standard), WebKit removing it could also be seen as a FU to Google.
Very funny.