First off, the 40mm is an AP shell. It is not HE. If you can land HE shells in the turret of a Wirbil, or Osti you'd be much better. Besides a sniper shot, the 40 will only penetrate the turret from the outside.
The HurriD is one of my favorite rides. And to be honest, I don't go for AAA vehicles at all. With the slow nature of the HurriD and no notable strength of frame, the reward isn't worth the risk. Especially to get off a shot you have to be aiming right for the AAA's gun.
As for your source, I am positive they got the IIC and IID mixed up, at least in gun loadouts. 4 20mms and 2 40mm's on similar planes is easy to get confused.