There is no bug here and I will explain.
Apply to children is an option only available on the edit category screen for a category. So yes you can initially create an additonal field and have that applied to all children if you want sure. That is the only thing you can do.
If you double check you will notice that the edit and subsequent delete checkbox which is on the actual edit additional field screen are not the EDIT CATEGORY page. Your totally somewhere else. There is no apply to children box on that page, your only editing or deleting the actual additional field your working with as that page shows your working with.