I was at a friendīs garage today and we were looking at his 3rd Gen Pontiacīs motor.
As he is a tech guy at VWīs sister firm here Seat, I asked him why the coiled brake pipes, as per his Pontiacīs master cylinder/proportioning valve.
He told me it was to curb vibration and as a cooling aid for the pipes which were for the front discs, the rear connection does not have this.
The idea is, the front brakes, which are close, get hot and can heat the fluid up to the brake proportioning valve, if the line were just straight and 90š the heat could cause it to buckle, so the coil takes it better without distortion.
He also added that he has seen coils off the rear discs as well to dissipate heat without distortion to the brake line there.