Could be, it is also very likely that they just dumped it into the attic. On a cold day, run a load then go outside and see if you can spot any steam coming from a vent.
My house had the drier exiting into the garage, which is better than the attic but still bad. Although it did make the garage warm when we dried clothes in the winter.
The builders of my house DID dump the bathroom fans into the attic, with NO ductwork, just sat there blowing poop stink and moist air into the insulation.