In Macrium Reflect v7 and earlier, both ReFS and ExFAT file systems would appear as unformatted volumes. Creating images of unformatted volumes causes every sector in the volume to be copied. Although such images are perfectly good, they take a long time to complete and the image file sizes are much larger than necessary. In v8, we've introduce Intelligent sector copy for both file systems. This means that only used clusters are copied, significantly reducing the time to image and also reducing the size of the resultant image files. Additionally, MIG now protects Macrium backup files saved to either file system and CBT can be used to further increase the speed of Incremental ReFS images.
ExFAT Volume:
Macrium Reflect is one of only a very few imaging product that support Windows Storage Spaces. ReFS is the default and recommended file system to use with Storage Spaces.
https://docs.microsoft.com/en-us/windows-server/storage/storage-spaces/overview
Note: ReFS file system detection is only supported in Macrium Reflect Server and Server Plus editions
ReFS Volume: