For musicians, what are they doing with the chorus here?

Are they double timing on the refrain or doing something else? Also, would there be a reason other than sounding different that they would do it?
http://www.youtube.com/watch?v=QQvQVYbtpGA
A show from Osaka on that same tour. The song sounds different again (to me at least). Were they just experimenting?
http://www.youtube.com/watch?v=ReoIPENpHUw
http://www.youtube.com/watch?v=QQvQVYbtpGA
A show from Osaka on that same tour. The song sounds different again (to me at least). Were they just experimenting?
http://www.youtube.com/watch?v=ReoIPENpHUw