This cannot work as restic never check the contents of a folder that is excluded. That is if you exclude /my/subfolder then negative patterns within that folder (e.g. !/my/subfolder/config.xml) cannot work.
See Allow excluding/negative-excluding directories only – give meaning to trailing slashes · Issue #4399 · restic/restic · GitHub and Only include some specific file extensions in backup for a more detailed discussion of that behavior.