Adding a caption add file unintentionally to watchlist

Steps to reproduce:

1. Enable, if not already done, the option "Add pages I create and files I upload to my watchlist" in your preferences (watchlist section)
2. Load a file without captions
3. Add a caption in a language of your choice
4. Result: File was added to your watchlist even that you have not created the file/file page

Expected result: No change of the watchlist status.

My interpretation of this behaviour: Creating a first caption is handled as page creation. And this is wrong.