The node you see is not actually a changelist, and there are no changed files inside it. It lists files that, based on your project git history, are usually changed in the same commits as the files in the active changelist, and appear related to the changes you applied.
The purpose of this node is to suggest some files you might want to change and commit in addition to already modified files, so there is no need to amend or create a new commit with these changes later if the files do need to be modified as well.
If you don’t want to see it, just disable the Show files related to the active changelist option under the Eye in the Local Changes toolbar. Disabling the ChangeReminder plugin would also work, but is unnecessary.
