I only ever heard "Full ahead" and it was generally the instruction that the "Old Man" or whoever was in command on the bridge, gave to the Deck Apprentice or Junior Deck Officer standing-by the Engine Room Telegraph. This was rung on the telegraph so that the Engineers could bring the main engine up to the revolutions that had been established when the ship was built as correct for that command.
Once the ship was clear of land, the pilot had been disembarked to his launch and there was no more shoreside interference we would get "Full away on Passage" which was rung on the telegraph by swinging the indicator round to "Full ahead" twice, to which we would reply in the engine room by two enthusiastic swings on our telegraph. Following that the Senior Engineer (Chief or Second) would leave the engine-room to the watch-keeping engineer. Boiler tubes would have to be "blown" to clear them of the soot that would have accumulated during the time in port. The stand-by steering motor, boiler feed-pump, and generator would be shut-down. The sea-water evaporator would be flashed-up to start replenishing the fresh water tanks and various adjustments would be made to things as H.P. & L.P.Extractions, Turbine shroud clearance, Gland steam and a myriad of other things, all the while bringing the main engine full sea speed.
I am sorry this has been such a long-winded post, even so I have skipped a lot that occurs when "Full ahead" is ordered. I hope it shows just how irrelevant "Full steam ahead" would be certainly on a Merchant Ship.