No one seems to have mentioned the fact that the THS can be moved manually to control the pitch at all times, even in flight.
The aerodynamic authority of the THS is way in excess of the elevator authority.
This fact was very obvious while conducting Upset Recovery Training in the sim when use of the THS greatly speeds up the recovery action.
Just because it isn't touched after setting the take-off trim after start doesn't mean that it can not be used in flight.
No Airbus manual will say this however.