This is technically a two part question. It would be normal operation if you are braking and bumps or the road surface cause a loss of traction and ABS activity results. It is also normal to have a change in pedal feel DURING an ABS event. Depending on the model and year the brake pedal may fade slightly and or rise a little and feel hard during the event.
So my question to you is the change in pedal feel only during the ABS event or afterward and for how long?