are you saying the quickstart package once installed can not be updated?
Quickstart pack is actually a complete demo website and an entire Joomla package containing the CMS, components, modules, template, other necessary data, and configuration.
So when it comes to updating, you can update the template and framework. It is not necessary to update the content inside. If there is any related extension, you can update that as well. So all these are done separately.
Hence, you can update everything in the Quickstart as I mentioned, but if you mean that you want to do a one-click update of the package, then that is not the case.
Hope it's clear now.