That's more likely to be to do with the operating system the server running Moodle is using.

All operating systems - except Windows - are case-sensitive and therefore see pic.jpg and pic.JPG as different files...

Of course you should not read anything at all into the fact that a Microsoft program exports a file with an upper case file extension when lower case is the convention, oh no.

You should always make all references to files and folder case-sensitive as you never know what kind of server it will end up on - particularly with SCORM-based e-learning which is expected to be very portable. We see so many 'broken' courses that just haven't been checked on a case-sensitive server.