Published airport schedules are on/off stand times and not landing take-off/times. So for the STA1130 a landing time of 1120-25 is on schedule. If the ATA of 1104 was the landing time then the flight was 15-20 mins early.
Handlers often work in teams being allocated flights where flight timings allow them to move from one aircraft to the next. So it's possible the early landing meant the team were still busy handling another flight.
Stand availability can be a problem at peak times when arriving aircraft land early on the schedule as often the allocated stand is still occupied by an aircraft not yet departed. this creates ground congestion problems for ATC and the allocators often having to park the aircraft somewhere else then this messes up the aircraft handling plan.
So while landing early may be nice for the passengers and crew it can often seriously affect others on the ground.