blowerdoor is done at high pressure to compare one house to another. we can estimate real world leakage rates by comparing that to the weather. for eg roughly 5ach@50 pascals = 0.35ach air leakage.

A lot of the blower door leakage measured will only apply to a internally pressurized situation but not in balanced (weather or BPV) situation i.e. leakage through sockets and light fittings, cabinetry, etc...

think of a box with 2 holes, 10 liters in and 10 liters out. then add a ppv with a third hole pushing air in 10 liters, which goes out at 5 liters through both holes. 

Nah, you'd have 10 litres in from 2 holes, and 20 litres out. Adding internal pressure will not reduce your reduce your outflow from +10 to +5 in one hole and at the same time increase from -10 to +5 from the other hole

with a bbv you have 10 liters in/out through the two holes and also 10 liters in/out though the bbv, making it 20 liters through the box. 

So you are getting additional airflow through less heat loss, sounds like the entire purpose.

air flow dries.

Nah, dry airflow dries. Moist airflow moistens. Hot airflow heats, cold airflow cools.

ppv normally turns off at high temps or switches over to a outside air source (summer vent). they slow down in cold weather but must keep going otherwise hot air will go back up in reverse and cause problems. 

outlet pouring cold air onto you means they put the vent in the wrong place. it should never be above seating/beds etc.

Agreed. On a cold night PPV has to pump in cold air in order to prevent condensation. Which then needs to be countered by adding heat, which is then being forced out of your house with no recovery.

ppv turning off is not good for airflow and bbv is far better in that regard.

Agreed

PPV compensates that a bit by blowing in far more air in during times when temps are better,

times when opening a window would suffice

you really need an airtight house to make effective use of a bbv. 

And yet my condensation is gone, my airflow in the house is increased 24/7, no uncomfortable locations due to cold/hot vents, and the additional heat loss is measured minimal.