I think I understand what you are doing now.
You are adding a Leader to a Symbol in the Project, and that Symbol Family's Line Work is assigned to a custom Subcategory which uses a thicker weight than the Generic Annotation Leader Line in the Project.
I have a suggestion for you that you may like better: Don't change the Symbol Line Work in the Family. Leave it on the Parent Category and using the Parent Category's Line Weight and Pattern. Instead, use Overide Graphics in View: By Element(s) to change the Line Weight of both the Leader and the Symbol together. You could even set up a View Filter to do this.
I can readily see where changing the Category Line Weight for the entire View could be problematic.
FWIW