promise Are you suggesting that I the site (using the quickstart) by overwrting the flies via ftp?
You can simply download and install the latest template version following instructions/process which are similar to installing Joomla extensions globally
Quickstart package is installed on clean folder with new database thereby, deeming it as fresh install as it already contains all the prerequisite joomla core folders and files so it wont install or get reinstalled on already running Joomla site
More details on quickstart package can be referred here
Upgrade Method:
You can install new version directly over this template version which had come compiled with Quickstart package. Uninstallation is not required.
Do ensure to take backup of your site before performing aforesaid steps, in case rollback required whilst facing any issues e.t.c