As I only check for the filenames as they are provided by the system and for the reference string that is mentioned in the files - I assume yes, it might be because of that.
Edit:
Just checked for the official statements for this issue.
For official files it is clearly case-insensitive (http://www.ldraw.org/article/512.html)
For the fileformat itself nothing is stated (http://www.ldraw.org/article/218.html)
Given that situation it make sense to check the unofficial files with case sensitive comparison because on unix systems there is a difference for these.
Edit:
Just checked for the official statements for this issue.
For official files it is clearly case-insensitive (http://www.ldraw.org/article/512.html)
For the fileformat itself nothing is stated (http://www.ldraw.org/article/218.html)
Given that situation it make sense to check the unofficial files with case sensitive comparison because on unix systems there is a difference for these.