Is it the reviewers' responsibility to change the batch to lower letters. Or review it and submit it as is??
In computer programming terms, changing the text like this is very easy. I would not be surprised to learn that as the indexed data is entered into the database anything like this is fixed so that the searches of the database can be done more easily.
It would be useful to know whether that happens or not.
No, you do not have to change the batch to upper and lower case letters. While it is the desired way to index, it does not matter. Alan is correct. FamilySearch does run a program that will change those prior to publication.