URLs in WordPress are case insensitive by default. Because of this, some pages can be duplicated in cache, for example:
https://yoursite.com/mypage https://yoursite.com/MYPAGE
If you would like to avoid these duplicates you may need to enable Case Insensitive URLs feature.
If you are using Auto Warmup Table source, and enabled Optimize Prebuild Only (which is recommended) you don’t need to enable this option.