Q: Is a WHF considered to be used as "ventilation" or "forced air system?"
A: If by “ventilation”, you mean IAQ ventilation for the purposes of meeting ASHRAE, 62.2, it is NOT that.
If by “forced air system”, you mean forced air mechanical heating and cooling system, it is NOT that either.
It is a different beast altogether. It falls under the category of “ventilation cooling”. Which is bringing in cool outside air to “pre-cool” the thermal mass in the home so that the air conditioner will not come on so soon while the outdoor temperature rises.
The blower door test for WHFs uses the blower door to match the pressure inside the house that is created by the WHF and measures the CFM required to create that pressure. Because it is just pressurizing the house to a target pressure (-10 pa plus or minus 5Pa) that is well within it’s range, it is really just a variation on the blower door test. There should not be special approval required for this.