[Simon J]

While I could see that an ignition controlled power supply would be desirable for releasing electric brakes, are such brakes legal in Europe?

As for powering a fridge or battery charging, in both cases it would surely be undesirable to have these in action before the engine was running? It seems odd that these two pretty standard caravan features require a modification to the towbar electrics to make them work properly when they could easily be incorporated into the trailer module.
P.S. And when I think about it, you’d probably want the engine running before releasing electric brakes.