This is to accomodate the case where other directories than "ol" include "api" annotations. For example, the Swisstopo geoadmin folks extend OpenLayers 3 in an ol3 fork, and they have their own "ga" namespace/directory under "src". See https://github.com/geoadmin/ol3/tree/master/src.
This task generates build related metadata for the library based on doc annotations. Since it is about more than writing out exportable symbols, it makes sense to have a more general name.