What type of diagram is this … ? Is this a legal UML diagram?

I have received a screen shot of what seems to be UML diagram printout (to re-model it).

The diagram heading in the top-left shows “composite structure”.
(And that is the reason why I called it a UML diagram.)

All the major elements of the diagram are packages. Some are packages within a package.

I don’t know why the author used package elements instead of class or component element.

Anyway, does the above describe a legal UML diagram?

Thanks