Beaufighter: why isn't the rear observer position usable?

[Polybius]

The beau has absolutely no rearward visibility. To remedy this there is a rear observer sat in a little bubble at the back of the plane however it is not usable by the player. We can see him sat there in third person but can't swap seats from within the plane to have a look around. Not having any rear view is somewhat crippling and being able to control the observer would go a long way towards making the beau more viable and realistic on closed pit difficulty.

Is there any particular reason why we can't use the seat or is it just an oversight?