Outwest
My recollection is that nobody said that it was impossible, just that it had never happened and as the operator is one who supports the idea of NOT arming the floats over water as a general rule I am guessing that they were switched OFF at the time. In which case there was either finger trouble or a manufacturing defect or some other screw-up because this IS the first such incident.
Nonetheless flight testing in this way is, as you say, rather unorthodox but welcome anyway. Does that mean that folk will now follow the FM recommendations and arm them over water?
G.