When the list of checked updates includes dependencies (e.g. a kernel update), a confirmation dialog appears listing "additional" packages that will be installed. However, these packages are already in the list of updates checked for installation. The dialog is thus unnecessary and superfluous, because these dependencies have been marked for installation anyway. It's also confusing, suggesting that extra packages not in the list are going to be installed, when that is not the case.
The dialog is not present on the PackageKit backend