I think that’s a superficial take. For instance, elsewhere in the documentation it says Lemmy can also function as a blogging platform. … (see here). Moreover, at the beginning of the documentation it says Lemmy is a selfhosted, federated social link aggregation and **discussion forum**. (see here).
Not that the documentation defines what is possible on the platform … its features do.
Beyond that “link aggregator” is a generic term for reddit-like platform, and can often implicitly include all of the interactions that don’t include linking to external sources.