I am not familiar with your particular car and do not have access to a diagram at work but 2 thoughts do come to mind:
1. Some switches have 2 stages. when lightly pressed they will activate the brake lights (say under light braking) but then when pressed further they have a secondary contact point that grounds the solenoid.
2. Some vehicles have separate switches for the 2 functions.
Both force the driver to provide sufficient brake force when placing the vehicle into a drive gear.