Sorry for misleading you about your --files-from option. Of course this is equal to just putting all paths to the command line.
In your case the problem is that
/data/www/*
/home/nexargi/GI/mysql/*
resolves the paths to all entries within this dirs. So if files or dirs within those two dirs change, you have changed backup paths and restic will not find parent snapshots.
Try using
/data/www/
/home/nexargi/GI/mysql/
instead. (The same could be achieved using the PR above, but you are right this is still experimental)