As a fact, since the road layout was changed to its current form at this location there is only one GSV view showing cars parked, and one of these is clearly displaying a Blue Badge anyway(which, OP, is an exemption), the other view is unclear.
OP, I suggest you forget this as a substantive defence(it's a stiff test requiring proof, not supposition as in 'surely this proves non-enforcement?'). IMO, the only purpose in raising it is to get into procedural territory to see how they respond.