In Revit 2023 when you start a new project with no template assigned most model categories have the built in subcategory <Hidden Lines>.
If you open a blank Detail Component family file and load it into the blank 2023 template, it brings subcategories from previous releases of Revit with it.
e.g. Furniture Category - In a blank Revit 2023 file the only subcategory is <Hidden Lines>. But load in a Detail Component family using the OOTB R23 template and now Furniture has <Hidden Lines>, Hidden Lines, and Overhead Lines.
"Hidden Lines" and "Overhead Lines" seem to be relics that still exist in the Detail Component family and can't be removed by the user. It would be good if these old subcategories could be removed from the family template files.