Why are Blocks useful when updating a batch of rows in UITableView?

So I am learning about blocks now and as I was watching a WWDC video I saw one of the demos using "update blocks" to update a batch of rows in UITableView.

My question is, why are Blocks u开发者_运维百科seful when updating a batch of rows in UITableView? What would happen if blocks were not used?

I'm guessing (I haven't watched the video, don't really know what this is about) that using blocks in this case is an easy way to have the update be done asynchronously - i.e. without the UI blocking and the user experience being screwed with. I doubt this'd be actually noticeable for simple table cells on a higher-end iPhone, but I can see this make sense with complex cells, especially if you can see more than... eight or so like on the iPad. You get the new data without the UI locking up.

But that's purely theoretical.