When using an Arch-based distro and the update process displays a log viewer in the bottom of the window, its scrollview continuously scrolls to the bottom automatically. This makes it impossible to scroll up to view prior messages while the process is still underway, because the moment you scroll up it scrolls the view back to the bottom again. It's very annoying. The scrollview should only automatically scroll to the bottom if it's *already* showing the bottom/latest line.
The log viewer is only shown for PackageKit-based updates on Arch-based distros, and the Arch folks don't recommend using PackageKit anyway. Discover itself even warns you! So probably UX improvements here are not worth doing, given that the core experience is unsupported and un-recommended.