Currently, if we upload assets - abc.pdf and ABC.PDF - They are treated as different assets in AEM (Your local machine's storage parses it in case insensitive manner) The JCR stores the nodes abc.pdf and ABC.PDF as 2 distinct nodes. Most storage systems even in different OS (Mac | Windows) store files by default in case insensitive manner.
The assets are treated as different due to their case difference.
The assets should be treated as similar and versioning popup should be displayed.
Environment Details (AEM version/service pack, any other specifics if applicable):