Are you sure this isn't just to introduce some artificial delay to make it seem like it is "processing"? Imagine a slot machine that gave you a result in 10ms as opposed to rolling around for effect.
Looks like they're just causing computation and JIT'ing in Chakra and V8 before moving to the next square. SunSpider is a terrible metric and they're just poking fun. Pretty funny when you think about it.
