In short, yes you need to determine yourself if a sound is occluded/obstructed via a ray cast or some other means. We do not yet do emitter-listener visibility checks via the geometry sets, however this is something we may look into for a future release. The purpose of this funciton is mostly to position the sound, when it is behind portals, in the correct place via "virtual positions", but also provides some occlusion values based on the number of enabled portals vs total portals, connected to the room. You call the function after having already failed the visibility check.
In the future, this somewhat awkward function will most likely be deprecated in favor of internal positioning of the sound emitter.