Hm, to add to my response from another thread,
backing up config files is always recommended when the software may change these files. As explained, that’s the case for the databases of darktable and the changes during an upgrade may mess up the databases and therefore it is recommended to be able to roll back. If you already have a reasonable backup routine, e.g. daily backups, this may be redundant. Be aware that not every information will be in the xmp files, some is in the database only (I remember the time correction for geotagging and the groups, and the styles of course, but there may be more).