It all looks correct to me. Have you tried using series or authors instead of tags to see if that works?
Any collections created are deleted when you change that field, so it wouldn't clutter your machine with unwanted collections after testing. If I set Tags in that field I get 1200+ collections, but as soon as I change it back to series it drops back down to 58.
This would at least tell you if collection creation is working properly. If it is then it wodl narrow the issue down to something in your tags