Cart ... Horse
Kobo is the horse
Calibre is the Cart
When they change the horse, Calibre developers have to figure out it happened, adjust the supported FW version list (and make other needed changes in rare cases).
The message is mostly a warning that there COULD be changes needed to prevent corruption. Best to check the Kobo forum and see if there is any discussion of that NEW

firmware (bugs do happen, but there are a LOT of Kobo users, so issues should be noticed very soon)