The idea for max autobrake is to reduce the speed below the dynamic hydroplaning speed as quickly as possible. On water contaminated runways, the water is usually not of uniform depth along the runway, so the aircraft will run through good and bad sections, you need to maximise the breaking on the good sections. Remember also that autobrake gives a decelration rate, not a brake pressure, so using the reverse thrust will relieve the load on the brakes at any setting.
Interesting article, GlueBall, the "steam cleaned or sandblasted" comment would tend to indicate reverted rubber hydroplaning, but there is no comment on the tyre condition.
While the "the airplane's autoland system continued to attempt to correct the ground track of the airplane towards the centerline of the runway." the reverse thrust was still in operation. As the aircraft began to point towards the runway centre line, the reversers would actually be pulling the aircraft off the runway - the recommended procedure is to reduce reverse thrust to idle in this case, remaining distance permitting (at least it was in my airline).