[My first solution, apologies if it is too waffled!]
This wouldn't unlock for me with the above solutions, or the one proposed in the walkthrough.
It seems the game classes the 'choice' of dialogue you get with Gorilla in the first cutscene (if you just let the game autoplay) as you choosing the dialogue.
I found a route where you are never offered a choice of dialogue in the cutscenes, just scripted conversations:
Level 1 - Keep right.
Intermission 1 - Nothing.
Level 2 - Keep left.
Intermission 2 - Nothing
Level 3 - Nothing
Make sure to press nothing on your controller except your
to steer and
to speed up, and you'll finish the route in a fast car (I used the Police car) in around 5 minutes.