I'm a high-timer, but never flown FBW.......
We all know that the most energetically flown manual approach can sometimes be followed by a totally unexpected smoother-than-smooth touchdown on to standing water in (maybe) a howling crosswind. Even though it is not what was intended, and on an ordinary day on to a dry runway is a "landing to retire on", even so it happens, the water is not penetrated by the desired "firm" arrival, and the tyres aquaplane to a greater or lesser extent. Given that this aircraft never decelerated significantly, is it not just possible that the lightest of touchdowns (no WOW sensed, and maybe one mainleg at a time), plus significant aquaplaning which may not even have allowed the wheels to spin up, thus never triggered any/most of the logic conditions required to deploy any/all of the retarding devices OTHER than to allow reverse thrust?
Just my pen'worth, as this does not seem to have been considered thus far............