I think I recognized a bug within the taglist field. I tried to reproduce the issue in the test plugin and had the same problem:
Create two new tags with the same name within Posts / Tags
Create a new Post and add the newly created tag (just one will appear since they got the same name)
Check the table “october_test_posts_tags” and you see entries for both tags, even if you got the feeling you just selected one.
Even if the tags have the same name, I would expect them to appear twice in the taglist dropdown and only one relation record to be saved.
In my example, I got a tag / node system which is all saved in the tag table. Now within this relation field, I only allow to use tags. But even if I filtered the allowed tags in my taglist field, I still got the relation entries for both tags (or the tag and the node) after saving.
I can imagine several more situations in which this could definitly be missleading, so I hope for a quick fix, so that the relation cares about what’s filtered for this field and only sets those as a relation table entry.