The way they have gone out of their way to deliberately remove the functionality could be argued to cause damages to people who are using the unsupported functionality.

There is no "downgrade" path from btrfs to ext4. Users have to move all their data off the NAS to some other storage, delete the btrfs volume, create a new ext4 volume and then copy the data back on.

These alleged damages are measurable in both time and the cost of storage rental.

Even worse, if you apply this upgrade without knowing that you need to do this procedure, your data is inaccessible until you contact customer support.