"Are you 100% sure that ELAC simply pitches down the aircraft?" What else do you think it could do?
When high speed protections activate, the elac commands pitch up to prevent excessive overspeed.
The protections are just maximum/minimums that the elac will not allow the plane to exceed, regardless of thrust setting, stick input etc. Once the speed is within the extremes again, the protections are not active and the plane returns to normal law.