it is very good idea to keep all your DNS records downcase, because DNS
is not case sensitive. What is the reason to have upper hostnames? Like
to warn you that this is a production system?
Anyway, it does not matter if you type ABC.example.com or abc.example.com. If you need to have some sticky information like flags
with your host records, raise a feature request for it.
> My question, Can I do this change.
Better to ask on the devel list, you can at least try to file a pull
request with that change and we can discuss it. For myself, I tend to
prefer sane defaults, but this could be optional (option in global
settings like "Allow upper case host names" could be fine.