For the failure of ground spoiler case only:
Once the nose wheel has been put on the ground, if you pull back on the stick, you are generating downforce on the tail and therefore, a rotation around the main wheels, where possible. This is likely to unload the nosewheel oleo and either lift the nosewheel back into the air, or at least attempt to increase the angle of attack of the wings. This will keep the lift generation of the wings going and thus reduce the effective weight on mainwheels. Braking deceleration is a function of weight on mainwheels.
Was the Airbus design logic to build in ground spoilers and deploy them on landing to minimise the ground roll for contaminated runway operation, or was it to reduce any lift generated with the nosewheel on the ground in normal operations (or both). I have no knowledge of the effective wing AoA on the ground.