Default Custom Components in project have Library counterparts

Steps to reproduce:

1. Create a new URP project.
2. Assets > Create > UI Toolkit > UI Document, open this in UI Builder.
3. Note under Library, in the "Standard" tab, there are Tab and Tab View controls available.
4. Under Library, click "Project".

Actual results: Custom controls TabbedView and TabButton exist here.
It is confusing that it is in the Project view by default, as I didn't create these as a user. I also can't find documentation for them.

Expected results: There should be some existing documentation on these Custom Controls, or they shouldn't be included by default as they seem to duplicate existing Library Controls.

Reproducible with versions:

• 6000.1.0a6, 6000.0.29f1
• 2022.3.52f1, 2021.3.45f1, but Tab and Tab View are not available controls in these versions so perhaps these make more sense here.

Tested on (OS): MacOS Monterey 12.7.4

Notes:

• I looked for some documentation on these components, but could not find anything. I did find a thread expressing confusion over these components https://discussions.unity.com/t/how-do-i-even-use-this-tabbutton-and-tabbedview/913059
  and felt the same way about them.