Yeah it turned into that before kinda dying. Now in the "real world" those tools are only used for diagrams that explain what's called a "slice" of the architecture, but no one really gives a whole architectural view of a system on UML. Not even for a simple component.

But the glimpse you got of it as an undergrad was UML trying to give it's last kick before dying. The whole quest for a formal definition and a standard for it doesn't make sense if you only want to use it to give an architectural level view.