Agaricus,
The reason he may have called fully ready would be if he had been asked to "report fully ready"(OMG - how cringe making - Ar$e) a regular occurrence at many airports. Furthermore it is (depending where you are) a display of airmanship and common sense to call airborne in LVP's. Or if you are on the ground watch the TCAS for the aircraft ahead to get airborne (remember Linate).
Ivor