Well, there have been a number of changes to this template since first created. This is what I believe has happened.
This code is in the current ja_purity templateDetails.xml file:
The first file is located in the language/en-GB/ directory of the front end.
This file contains the translations for a number of items. e.g. site slogan, font sizing etc.
The second file is located in the language/en-GB/ of the back end.
This file provides the text for the pop up mouse rollover field descriptions while you are trying to figure out what the template settings are supposed to do.
I have removed the above lines from my templateDetails.xml file and everything still works. It appears that the Joomla core knows where to look for the en-GB.tpl_ja_purity.ini files based on the use of the ja_purity template. The other stock templates also provide similar files at the same locations even though they may not list the files in their templateDetails.xml file.
USER NOTE: If you are going to change the name of the ja_purity template to something else. e.g. my_ja_purity, and if you still want to have the rollover functionality plus the various slogan text fields etc., make a copy of each of the en-GB.tpl_ja_purity.ini files and rename them to en-GB.tpl_my_ja_purity.ini.