Did they ask Mike Rowe to re-do some of the season 2 episodes??

I watch a lot of these on you tube & I noticed that the episode about the asteroids was narrated by both Dellums & Rowe. Does anyone know if Mike Rowe was asked to re-do all the episodes from season 2? I put the 2 episodes on 2 different computers & ran them at the same time & the show was done word for word by both. I am just curious. Thanks.