No, this is something different. It means that when exact search is on,
writing "ta" would be enough to display, say, notes having one of the tags "task", "talk", and "notable".
If you want a mixed tag-text search, please write a separate request for that! Thanks

If you delete the "tasks" tag via middle-clicking on "tasks" (or pressing F4 and writing "tasks" into the second edit box), the tag selection stays.
After editing a note tag selection is reset for the purpose of following the UI guidelines: "you must see what you've just edited". If tag selection was to stay, the note would disappear.
It can probably be made into an option, but I haven't come up with an elegant way to do it without complicating the UI.