Grown historically.
In 1.5, it was not translatable. We had for example:

<install type="component" version="1.0.0">
<name>Module Manager</name>
<author>Joomla! Project</author>

In 1.6 was introduced the Translation of the extensions name and, logically, lowercase was used and strtoupper in the JText for core extensions.

<?xml version="1.0" encoding="utf-8"?>
<!-- $Id: modules.xml 20196 2011-01-09 02:40:25Z ian $ -->
<extension type="component" version="1.6.0" method="upgrade">
	<name>com_modules</name>
	<author>Joomla! Project</author>

I am closing this as it is not a bug. ;)

@infograf768 Many thanks.