UPDM — Section: 8.3.4.3 ArchitectureView Description

Description is confusing.
If the ArchitectureViews are Viewpoints, as described in the Viewpoint description:

"ArchitectureView can be used to implement the Viewpoint/View capability. As a UML Package, ArchitectureView is a nested construct. Using a CustomView, a new Viewpoint can be defined, and custom views can be defined within this new package. "

then the Views should not be subclasses of them. That is if OperationalView is considered a Viewpoint, then OV-1, a View should not be a specialization.
On the other hand, <<Vewipoint>> specializes ConformingElement that extends Class, so the ArchitectureViews, OperationalView, etc. can't be Viewpoints. So what is a Viewpoint?