To be quite honest I sure my phone already had this update. Got excited this morning when my phone said it was ready for an update. Thought it was gonna be denim...
well, I dont exactly recall what that button/link is called as.
It use to show right below the message "an update is ready to be installed" once you are done with downloading it.
But, yeah it does show the details
You also get details about the update after successful installation of updates, right after data migration step.