Stubby wrote:
That's fine because your attic is actually outside. The advice should
be to vent on the outside of your insulation layer. This way if you
dump a cubic foot of air at 100% relative humidity into the outside, the
RH of that cubic foot will instantly drop to very close to the outside
value. For condensation to form, the RH must be 100% on a colder surface.

Sorry, but that's incorrect.

Dumping high RH air into a cooler area, will INCREASE its RH, with the
rise depending on the attic temp.

Compounding the problem is reliance on passive gable vents, which by
themselves will have no airflow unless there's wind from one side or
the other. So, running bath vent will just displace attic air with much
higher absolute humidity air, which on chilling will see rising RH, as
mentioned above. (Outside air in winter is typically of much lower
absolute humidity than indoor.)

J