Control of a D.C. motor reversing contactor
The F/R contactor driver doesn't seem to have any function in normal operation, but what it does do is drop out the feed to the contactors in the event of a coil short - "Forward, reverse, and bypass contactor driver outputs are internally protected
against shorts in the contactor coils" from http://assets.curtisinstruments.com/Uploads/DataSheets/1204x05manual.pdf 

On the new arrangement such a short would only be dealt with by the control fuse blowing. This results in a loss of drive, on the old arrangement, there's the possibility of braking to a halt using the reversing contactor if the forward contactor fails.