Rick

ORIGINAL: Mobius
No.
They had it that was in the first go of PCOWS and vehicles moving through woods looked like Brownian motion. Random turns and jenks. Turning sides to enemy at just wrong time to get around a tree.
We can just assume the drivers are getting around the trees.
ORIGINAL: Stridor
Of course it is your game and you can do what you like Rick.
What I suggest is try making the trees vehicle obstrutions only (select this option in the MM for your autogen trees) (so as not to obstruct the infantry) and then see how the game plays out.
Check for things like the correct LOS through your "new" obstructing woods and see how your vehicles drive through.
I agree that there is not enough of a price to pay to have a vehicle drive through woods and there should be. Just like infantry climbing over fences seems to slow them down for just a nano second.
Regards
S