In accordance with the FCOM 3, supplementary techniques, the BSCU reset should only be done with the park brake set, as the nose wheel makes a full deflection to the stop during the reset. If this reset is done during taxi, you may well find yourself in the grass. The switch may be turned off, and alternate braking relied on without steering.
If this reset was done because of a nose wheel steering problem, it is "mandatory", according to the same chapter of FCOM 3, to be entered into the tech log and the aircraft returned to the stand.
I have no idea what happened in this case.