In recent discussion (in these forums) about arrival times, the figures were based on the 'Parking brake = Off' to 'Parking brake = On'.
The reason being that the action is noted electronically by the aircraft with the associated time. This action + time is also, for many carriers, immediately relayed (automatically) to the company so that their operations department and computers know the flight has 'arrived'.
Tthe figures were discussed in light of the predilection of one well known European LoCo to 'trumpet' their early arrival - whilst the machine is still taxying and, therefore, has not 'arrived'.
The point of this is that the company may know the time of touch down but they will also know the time of 'arrival'. Of course, you may then have a delay of 15 minutes before you can disembark, for whatever reason, and then you have to find out from the airport what happened! My guess in that situation, is that the airport will always point at the carrier and the carrier will point at the airport!
Do let us know what happens.